Because fuck eardrums, and guitar solos kick ass.
Heavy Metal began its unholy existance as a fusion of the technicality and improvisation of Blues-rock and the batshit-craziness of psychedelic rock back in the 60's, generally known as a period where a whole lot of fucked-up shit went down. As can be assumed in a period where acid, free love, and hippies were causing chaos in the streets, headbanging was pretty low on the list of "Shit That Worries Parents", so it managed to sneak by as just another trend in rock.
Then before anyone knew what was happening, everyone and their creepy old neighbors had the "Stairway To Heaven" and "Smoke on the Water" record or cassette or whatever the hell it was they listened to back then, and metal was "popular". Unfortunately this is also the same general time period in which Bellbottoms and platform shoes were considered "popular", so that doesn't prove a whole lot, but whatever. The movement was headed by now-hallowed bands such as Led Zeppelin, Deep Purple, Black Sabbath, and Alice Cooper, as well as mostly-forgotten groups like Iron Butterfly, The Jeff Beck Group, and Blue Cheer. Metal began its true split from standard Rock'n'Roll when Black Sabbath's lead guitarist, Tony Iommi, managed to hack off the tips of his fingers while cutting sheet metal. What he was doing cutting sheet metal, we'll never know (I hold to the belief that he was forging a battle axe or some shit) but the accident forced him to tune his guitar down a whole step (for the guitar-savvy, D-tuning) to loosen the strings and prevent further finger-mutilation.
How to become a metal God.
Forced to play with plastic tips on his fingers, he also began to use simpler, easily-held power chords, such as can be heard in Sabbath's "Iron Man" and Deep Purple's "Smoke on the Water". This style was furthered by bands like Kiss, Scorpions, AC/DC, and Judas Priest to form the outline of the true "Heavy Metal" sound.
The late 70's and 80's saw the formation of many of metal's greatest bands, such as Slayer, Metallica, Iron Maiden, Megadeth, Van Halen, Def Leppard, Motorhead, and plenty more. In 1987 MTV, still in its pre-reality show days, began airing Headbanger's Ball, a music video show devoted solely to metal that's still around today. This was just in time for the beginning of the Great Genre War (to be addressed in the next section), firmly assuring that no one will ever actually watch it for more than 10 minutes.
Today, Heavy Metal is gaining more acceptance and becoming "cool", as opposed to its previous brand of "scary as fuck", much to the disappointment of its most diehard fans. Many still hold that nothing can compare to the glory days of ...And Justice for All and The Number of the Beast, but it cannot be argued that metal is alive and thriving, and as hellacious as ever.
Sometime during the 80's, Heavy Metal began to drop under the public radar, as the genre began to trend towards a style far too extreme and awesome for normal radio and mainstream appeal. While it still maintained a strong following, the fans of metal tended to be much more devoted and passionate about their favorite bands and styles, leading to a fracturing of the core fanbase. Some favored the tamer, stadium-filling sounds of Motley Crue and Kiss, while others tended towards the darker, brutal moshpits of Slayer and Metallica, or the demonic growls of Napalm Death and Obituary. Thus began the Great Genre War of Metal, as various descriptive and obsessively-specific titles began to emerge for the different genres of Heavy Metal. To witness the the ensuing carnage, visit the comment section of any metal video on Youtube. In addition, you will quickly be made aware that this is also a case study of nearly all of the internet personality disorders; congratulations, you did science. A typical section looks like this:
metalfan10293 - "this vid is AWSOME i fukken luv metalcore!"
mulishaman - "THIS SHIT SUCKS FUCKERS NEED TO LEARN HOW TO PLAY LIKE PANTERA AND FUCKIN SLAYER HELL YEAH!!!!! \m/ >_< \m/"
jon1023948 - "fake!"
mettulhead - "um i think you mean deathcore, learn your genres"
kingmetal - "fuckin noobtards, this is clearly melodic grindcore with some power metal elements"
...and so on until your brain explodes.
(*note: all the above names and comments were made up by me, as I wrote this. If I inadvertently used your screen name here, may I kindly direct you to my comment box where you may leave a complaint.)
Each genre of metal is the result of mixing influences from other genres and bands, just like what you see in every piece of music ever. For some reason though, metalheads -not normally known for their powers over "words" and "thinking"- feel the need to create a new sub-genre every time a band uses a different guitar. Every single one of them is apparently a qualified fucking Ph.D. on the subject as well, so fuck you if you try to correct them.
That's Doctor Metalhead to you, sir.
Purely because I am one of the greatest human beings (and non-human beings for that matter) of all time, I will attempt to break down some of the most significant sub-genres of Heavy Metal. Further awesomeness on my part will also be provided, as each bands name will link to their MySpace Music or equivalent site. You're welcome.
Yes, this qualifies as a subgenre, because I say so. This is metal at its most basic and purest form. Distorted and clean guitars; long, technical solos; high-pitched, wailing, clean vocals; occasional but not pervasive double-bass-pedal drumming. This is the metal that people used to be afraid of, now falls into the "slightly more intense than Nickelback" category. Typically tries to make up for this with frightening album covers, flashy stage theatrics, or just plain crazy (see image below).
Ozzy Osbourne: here to consume your soul.
One of the most iconic subgenres of metal, Thrash emerged back in the early 1980's and is still the drug of choice for many metal purists. Typically features a varied vocal style, ranging from singing to dark growling; songs are backed by absurbly fast drumming, with machine-gun style double-bass; speed-picked guitars with technical and fast solos; fast bass, fast vocals, fast women, fast cars...did I mention this shit is fast? Some of this sounds like you gave the Flash a Mozart Concerto and an electric guitar, and let the shit go down. Apparently the vocals tend to talk about a lot of societal and personal issues, but I never really noticed.
Shreddage, courtesy of Kirk Hammet. With not-Cliff-Burton and the Napster-Killer in the background.
Widely considered to be the most intense of all metal (to its credit, it does have "Death" in the title) Death Metal emerged in the mid-80's as a spin-off of Thrash. With a much more underground following than its Thrash and Heavy Metal brethren, it is characterized by extremely dark subject matter and sound...essentially the closest thing you can get to the soundtrack of Hell.
Boo! Rawrrr! Scary!
Musical characteristics include heavily distorted, shredding guitar work; deep, guttural growling/screaming vocals; lots of double-bass, though not quite to the level of thrash. Like eating live octopus, it is an acquired taste, though a lot of people just don't acquire it, nor do they particularly want to. And if you eat live octopus, that's disgusting, just thought I should note.
Black and white and metal all over.
As any metalhead will tell you, Scandinavians know their fuckin' metal. Probably something to do with the level of badassery that went down back in the Viking days; an imprint on their collective souls that just makes them naturally adept at shredding, draws them instinctively to long hair-wearing, and gave them a geneology that has bestowed them with necks naturally resistant to whiplash and other side effects of headbanging. In the late 80's the American Death Metal movement found its way to the shores of Sweden, most likely on a fucking longboat cause that's the metal way to get shit done around there. Three bands - Dark Tranquillity, In Flames, and At The Gates - took it and perfected it, adding distinctive elements of melody and harmony into the harsh tones of Death, and thus Gothenburg Metal was born. This style has become increasingly more popular, as it combines the brutality of metal with catchy melodies and guitar hooks, and if you can't tell by now it's my favorite, so deal with this overly-glorified explanation. Gothenburg, also known as Melodic Death Metal, is characterized by the same growling vocal style, distorted guitar, and double-bass of Death, but is distinguishable for its extensive use of keyboards, intricate melodic patterns, and dual-guitar harmonies. And yes, it is fucking awesome.
Death Metal may be the most extreme, but without a doubt Black Metal is the most fucked up. Deeply rooted in Satanism and other scary shit, I worry that even writing about it is putting me higher up on the Godly "Smiting List". It's dark, it's gloomy, it's doomy. Production in this style is notoriously bad, but for some reason they like it that way, and even long-established and popular bands continue to record in very low fidelity. I dunno, adds to the darkness and doominess I guess. More minor-key tonality than you can shake your fist at, coupled with overly-distorted guitars and growled, shrieked, or grunted vocals (that are somehow appallingly off-key, at least as much as a grunt can be off-key) make up the majority of this music, and you can bet your ass they do it all in enough black and white makeup to put Gene Simmons to shame.
Notable for their apathetic attitude towards their fan base, Gorgoroth vocalist Gaahl was quoted as stating that "black metal was never meant to reach an audience, it was purely for our own satisfaction". Well good for you, Gaahl. Please don't kill me.
*note: I just want to add that it seems a odd that Black Metal bands have Myspaces, seems out of line with their whole philosophy, but hey I don't judge.
If all that gloom and doom got you down, here's somethin to cheer you up!
They're metal and they're fabulous!
Welcome back to the 80's, when metal was just getting popular. When death metal and black metal dove underground to their crypts and similarly dark places, these guys were the face of metal to the world. I'm expecting a formal apology from the 80's very soon.
Glam Metal, often called Hair Metal (see above for 3 good reasons why) was probably the friendliest that metal has ever been. Championing loose women, flamboyant clothes, androginous appearance, crazy hair, and occasionally some music, Glam rockers sought to epitomize the tenets of "sex, drugs, and rock'n'roll". If you don't know what Glam metal sounds like, you clearly have no ears and probably shouldn't be reading this article at all. But to be nice, I'll explain: Glam metal is loud, absurdly catchy, and loaded with ridiculous solos. Songs like Def Leppard's "Pour Some Sugar On Me", Motley Crue's "Shout At the Devil", Bon Jovi's "Living on a Prayer", and Kiss' "Rock and Roll All Night" were and still are insanely popular. Guitarists like Michael Angelo Batio and Yngwie Malmsteen emerged during this time period, with some of the most insane guitar solos ever seen, and the hair just made it crazier.
Metalcore is one of the most popular forms of metal today, with even a few albums hitting the national Billboard charts. Probably now the largest subgenre in terms of number of bands, its name is derived from its stylistic fusion of Hardcore Punk and Heavy Metal, which came together in an unholy alliance sometime in the mid-90's. It is known for its screaming (with occasional clean) vocals, heavy use of double-bass drumming, melodic dual-guitar harmonies with heavy use of alternating high-low note patterns, and most importantly, mosh-inspiring, neck-snapping, bone-crushing breakdowns. Pioneered by bands such as Sick Of It All, Earth Crisis, and Hatebreed, Metalcore has also become a haven for many "Christian" metal bands, such as As I Lay Dying, Zao, Norma Jean, and Underoath, who use religious themes as inspiration for their lyrics, though they still do their best to sound like Satan with a sore throat when they sing.
metalcore is one of many "fusion" genres, and the root genre for hundreds if not thousands of other "___-core" subgenres. These include, but are certainly not limited to, Deathcore, Grindcore, Noisecore, Moshcore, Rapcore, Crabcore (not an official term, but people sure love to use it to describe this), and more that have most likely popped up in the time that it took me to write this.
Examples: Parkway Drive, Killswitch Engage, As I Lay Dying, All That Remains, The Devil Wears Prada, Hatebreed, Earth Crisis, Darkest Hour, Haste the Day, God Forbid, Lamb of God (these last two are disputed, but I'll put them here cause that's how I want to do it, see?)
A perfectly executed headbang in action.
Power Metal is essentially what you get when you give a young child every Metallica and Iron Maiden CD ever made, all of the Dungeons & Dragons game manuals, and then lock him in a room for 10 years. When he comes out, he'll probably look something like this:
Forsooth, we are metal.
Power Metal is known for embracing every hint of fantasy and sorcery ever mentioned in the formative days of metal and turning it into an entire genre. Songs typically consist of tales of valor, knights, dragons, sorcerors, hell there's even an entire album devoted to a J.R.R. Tolkein novel. Musically, Power metal is characterized by high, soaring vocals reminiscent of Medieval bards, and absurdly fast, tremolo-picked guitar work.
Industrial Metal emerged in the late 80's, a fusion of synth-heavy Industrial Rock and Heavy Metal. It has become relatively popular, with Nine Inch Nails bringing Industrial Metal to the mainstream scene in the U.S., and bands like Rammstein playing sold-out shows all over Germany. Industrial is distiguishable for its extensive use of synthesizers, drum machines, techno beats, and other electronic effects; other features include mostly sung vocals (though very gruff, low voices are favored), heavily distorted guitar and bass, and relatively simple, repetitive rhythms and melodies. Theatricality is a big trait here as well, with many bands performing in makeup or costume, with extraodinary (and most likely extraodinarily dangerous) pyrotechnics on stage.
...I think that qualifies as a fire hazard.
Another notable trait in Industrial is the size of the bands; it is not uncommon to see Industrial Metal groups comprised on two or three members, and there are even a few one-man-bands, most famously Trent Reznor of Nine Inch Nails.
No that's...that's not it at all...
This trend has made the use of electronic equipment all the more important to the genre, for obvious reasons.
That about covers the major genres (though I know plenty of purists out there will bitch about me missing one or the other, but they can suck it). Here I'll provide some examples of some of the other subgenres that I just don't have time to elaborate further on:
I'll add more eventually, if you see a blatantly missing genre mention it in a comment and I'll add it.