[Matt the Merciless]

Well I'll give you a list of what I like and you can see if there's anything you haven't heard of/like from it:
(excluding what was already mentioned)

Alice Cooper
Bloodbath
Dethklok
Devildriver
Devin Townsend (LOVE)
Dimmu Borgir
Disturbed
Dream Theater
GWAR (LOVE)
Joe Satriani
Judas Priest
Korn
Mastodon
Megadeth
Metallica
Opeth
Root
Scars on Broadway
Serj Tankian
Sonata Arctica
Static-X
Strapping Young Lad
Symphony X
System of a Down
Tenacious D
Testament
Wuthering Heights
3 Inches of Blood

And that about covers it.
There are a bunch of others I kind of like but not enough to list.