Death Metal: Death/Cannibal Corpse
Melodic Death Metal: Kalmah/Amon Amarth
Blackened Death Metal: Behemoth
Thrash Metal: Slayer/Destruction
Crossover Thrash: Suicidal Tendecies/D.R.I.
Doom Metal: Saint Vitus/Pentagram
Speed Metal: Motörhead (no matter what you say, Motörhead is Speed Metal)
Power Metal: Helloween
Grindcore: Napalm Death/Brutal Brain Damage
Progressive Metal: Enslaved/Opeth
Classic Doom: Black Sabbath
Doom/Death: Katatonia/Opeth
Viking Metal: Ensiferum/Amon Amarth/Bathory
1st Wave Black Metal: Mercyful Fate
2nd Wave Black Metal: Immortal (best Black Metal band ever)
Post-2nd Wave Black Metal: Anaal Nathrakh
Symphonic Black Metal: Emperor
Gothic Metal: Moonspell
Extreme Gothic Metal: Cradle of Filth
Folk Metal: Ensiferum/Amon Amarth/Finntroll/Eluveitie
Pagan Metal: In the Woods...
Industrial Metal: Rammstein/Kreator (part of Kreator discography have the Industrial feel to it)
NWOBHM: Iron Maiden
Classic Metal: Led Zeppelin
Sludge Metal: Mastodon/Cult Of Luna
Metalcore (pretty much the only good Metalcore band): Lamb Of God
Hard Rock: AC/DC and Twisted Sister and Mötley Crüe