www.mp3.com has a shite load of genras and sub genras. here is their list for 'metal'
Metal
Alternative Metal
Black Metal
Dark / Ambient Noise
Death Metal
Doom / Stoner Metal
Goth Metal
Grindcore
Heavy Metal
Industrial Metal
Instrumental Metal
MetalCore
Nu-Metal
Power Metal
Progressive Metal
RapCore
Spiritual Metal
Thrash / Speed Metal
Genras galore...
edit: most of these I knew, minus rapcore, spiritual metal, doom metal.. which I care less about.... But to keep in 'theme' with the thread, I DID know those others!