For those who want a good discription and bands on some (and should be all) of the categories of metal music here it is.
(Stolen from the IGN Metal Music Board)
Heavy Metal/Metal:
Heavy Metal, or Metal, is loud and fast Blues/Acid Rock without the Blues. It is aggressive, menacing Hard Rock. Though Metal is often crass and juvenile, its high speed riffage and soloing is often technically demanding on its musicians. Metal has subdivided and mutated so often during its almost 30 years of existence that it is largely an umbrella term now. Bands whose sounds were influential, (or derivative,) and big enough to typify the entire genre are AC/DC, Black Sabbath, Iron Maiden, and Metallica.
Speed Metal:
Speed Metal took the speed and DIY attitude of Hardcore Punk music and combined them with Metal’s precision, guitar solos and lyrical content. Speed Metal dominated Heavy Metal music for a large part of the ‘80s producing such superstars as Metallica, Megadeth, Anthrax and Pantera.
Thrash Metal:
Thrash was essentially a stylistic expansion of Speed Metal, with more varied tempos and greater emotional range. Heaviness and rhythm are still paramount over melody, and much of the punk influence remains intact - Anthrax, Slayer, Pantera, and Sepultura typify this strain of Thrash. But the genre also made room for more complex, classical music-influenced acts such as Metallica, Mercyful Fate, Megadeth, and Celtic Frost. The former group of bands eventually gave rise to both Death Metal and, arguably, Nu Metal, while the latter spawned Black Metal.
Death Metal:
Out of Thrash grew the morbid, intentionally inaccessible Death Metal. Cannibal Corpse, Kreator and Entombed are prototypical Death Metal bands.
Grindcore:
Grindcore is a combination of Thrash Metal (such as Slayer or Sepultura) and Industrial music (like Skinny Puppy or Ministry). Grindcore is loud, morbid and typically filthy. Major bands are Brutal Truth, Napalm Death, and Anal ****.
Black Metal:
Black Metal is a form of highly theatrical, dramatic, orchestrated metal that originated in Norway in the early nineties in reaction to the increasingly punk, street, non-theatrical bent of Death Metal. Black Metal Bands such as Dark Funeral, Dimmu Borgir and Cradle of Filth integrate gloomy synthesizers, strings, and complex arrangements, sometimes going far enough to be called Progressive Metal. Mythology and religion are central to Black Metal, as most bands are vociferously anti-Christian, often grounding themselves in Nordic or Pagan beliefs. The story of the more outrageously violent and shocking early Black Metal bands such as Mayhem and Emperor can be read in Michael Moynihan's excellent, thoughtful book, Lords of Chaos.
Doom Metal:
Doom Metal is generally very slow, very heavy, and very gloomy in subject matter. Archetypes include the first two Black Sabbath albums, but modern Doom Metal's biggest acts include Candlemass, Cathedral, My Dying Bride, and Eyehategod.
Funk Metal:
Combining Funk basslines, Hip Hop/rapped lyrics and Metal guitars, Funk Metal bands like Faith No More and the Red Hot Chili Peppers were popular skate-rock bands throughout the late ‘80s and early ‘90s.
Industrial Metal:
Slightly less abrasive than its bastard son, Grindcore, Industrial Metal fuses Industrial beats, sounds and production techniques with Metal guitar and vocals. Nine Inch Nails, Ministry, and early Marilyn Manson are big name Industrial Metal acts.
Hair Metal:
Hair Metal, a phenomenon concentrated in the mid ‘80s to early ‘90s, is poppy, commercial Hard Rock/lite Metal played by bands with an extreme image fixation. Permed hair, makeup and spandex pants were de rigeur for Hair Metal bands such as Def Leppard, Poison and Bon Jovi. Your girlfriend likes this ****, and you sing along to it with her in the car.
Nu Metal:
Nu Metal is the post-modern offspring of a variety of influences that came together in the 90s. Combining the look, feel, and macho attitude of Heavy Metal with stylistic elemets heavily indebted to Grunge, Alternative Rock, even Hip Hop and Electronic Music, Nu Metal is the sound of adolescent angst in its most marketable incarnation. Limp Bizkit, Korn, Disturbed and many other bands with similar looks and sounds are prime examples of this genre.
Rap Core:
Rap Core is a hybrid, fusing Metal guitars with Hip Hop style lyrics. Originally, most acts took their cue from Run DMC, who pioneered Rap/Rock fusion with tracks like "Rock Box" and later "Walk This Way," and AC/DC whose power chord riffage Run DMC, were sampling. Bands that typify this old-school Rap Metal style are Stuck Mojo and the Weapon Of Choice. Typically Rap Metal bands have a rapper or two, a DJ (who scratches but doesn’t provide beats), Metal guitars, and a live bassist and drummer who lay down Old School Hip-Hop beats. A new wave of Rap Core acts, more Public Enemy and NWA than Run DMC, and more Slayer than Metallica includes acts like Limp Bizkit, Korn, and Rage Against the Machine.
Dark Ambient
Dark Ambient seeks not to soothe but to disturb with its environmental background sounds, with acts like Tweaker, Meat Beat Manifesto, and SekreT.
Digital Hardcore
DHC or Gabber, is, primarily, Hardcore Punk/Noise made digitally. This stuff is very noisy and aggressive, yet vaguely catchy. EC8OR and Alec Empire's Atari Teenage Riot are prime examples.
Industrial
Industrial is harsh, pessimistic electro-rock with a sonic palette of abrasive, mechanical sounds. The genre takes its name from Industrial Records, the label that hosted Industrial pioneers Throbbing Gristle. Front 242s’ “Geography” is a masterpiece of the genre, and other Industrial bands include Ministry, Coil, Einstürzende Neubauten, and Skinny Puppy.
Guitar Rock
This is guitar-driven, guitar-centric Hard Rock. Usually instrumental, it showcases technical proficiency on the electric guitar. Steve Vai, Joe Satriani, Eric Johnson and Yngwie Malmsteen are major Guitar Rock heroes.
Progressive Metal ("Prog"):
A lot of groups that defy description are lumped into this category. Most sound nothing like each other, but share a penchant for writing challenging music. The music is highly technical with a lot of strange timing and expirimental sounds. I guess you could call it the thinking man's metal, because it takes a good amount of cerebral activity to decipher all that is taking place. The sound can be very mellow or very harsh, but is always unique. Bands include Dream Theater, Rush, Liquid Tension Experiment, and Symphony X.
Ethereal:
A relaxed and serene musical style sometimes more descriptively known as ambient Goth, and closely related to electronic. Uses the samplers and synthesisers of ambient and electronic, but lacks the fast, powerful beats and adds typically Gothic sounds, eg. plainchant, to give a darker and richer feel. Some ethereal bands are strongly medieval in style, for example Ataraxia; others, such as Lisa Gerrard's solo work, are more like a quieter and slower electronic. Sample bands: Dead Can Dance, Love Is Colder Than Death.
Doof doof doof:
House, techno, jungle, anything you can hear going 'doof doof doof' from three streets away on a Saturday night.
Proto-gothic rock (post-punk):
Gothic rock stems from the post-punk bands, namely Joy Division, Siouxsie & the Banshees, Killing Joke, Bauhaus, UK Decay, and others. The music that those bands performed was rudely aggressive and decadently depressive at the same time. Common to the post-punk bands, their sound was distorted and the guitars sounded harsh.
Modern gothic rock:
Modern gothic rock is a varying lot, making it difficult to put down a single criterion for bands to qualify. England no longer being an exclusive importer of gothic rock, the music styles differ according to the individual band's country of origin. Fine examples of to what extremes the modern gothic rock can go are Faith and the Muse, Die Laughing, Inkubus Sukkubus, Rosetta Stone, Children on STUN, The Wake, London After Midnight, Vendemmian, Nosferatu, Corpus Delicti, Love Like Blood, Two Witches, Sunshine Blind, Giant's Causeway, The Shroud, Black Atmosphere, The Garden of Delight, Mephisto Walz, Moonchild, and others. Some of them follow the steps of the early gothic rock bands (London After Midnight, Nosferatu), while others went into the fast and rhythmic rock with clear guitar sound and female vocals (Die Laughung, Inkubus Sukkubus, Sunshine Blind). As it has been said before, there is no common criterion for modern gothic rock bands, though it is evident that they are removed quite far from the original post-punk sound, becoming more melodic, employing synthesizers, drum machines, violins, cellos and female vocals. Still, a rock is a rock, and (fast) guitars are a must.
Synth-gothic:
Hard to define, this subgenre is similar to the electronic specimens of modern gothic rock; it includes the usage of samples. As a rule, the music is quite serene, reminiscent of the synth-pop peformed with a "throughness" that is characteristic of gothic bands. Fine examples are La Floa Maldita, Edera, Derriere le Miroir, Passion Noire, The Deep Red, Blind Passangers, Clan of Xymox and Alien Sex Fiend of the early gothic music fame.
DarkWave:
First forms of "DarkWave" music go back to the days of the Electronic pioneers like Kraftwerk, Front 242, Nitzer Ebb, New Order to the current likes of VNV Nation, Apoptygma Berzerk, Covenant, Neuroticfish, And One, Wolfshiem, and Syntec, to name a few. As the DarkWave scene grows into a more popular Underground genre, more new faces bolster the already burgeoning Darkwave culture, threatening to overtake the stale and mass marketed mainstream music market.
Hardcore/metalcore/screamcore/emocore/etc...
Hardcore, in essence, is the fusion of punk and metal. Starting in the late 70s and early 80s with bands like Black Flag and D.O.A., hardcore can be descriped as punk speed, lyrics, and simplicity combined with metal's diversity, downtuned guitars, and proficiency. The sound has diversified, spawning bands like hatebreed, earth crisis, and .hopesfall.. (Thanks go to Maarek_Stele for this entry)
Power Metal
Power metal crystallized during the mid-'90s, mostly as a reaction against the harshness and lack of melody in death and black metal. Though it sometimes incorporated the complexity of progressive metal, or the menace and growling vocals of death metal, power metal was essentially a classicist style, featuring killer fast riffs as addition to very cheesy vocals and lyrics. Power metal was primarily (though not exclusively) a continental-European phenomenon. Bands include Edguy, Lost Horizon, Iced Earth, Rhapsody, and even some Iron Maiden. (Thanks go to Clinton.1984 for this entry)
