Post-2000:
DragonForce (actually mentioned before, but I'm seconding it. They do rock big-time, and are taking the piss out of the scandinavian power metal spectrum by going cliche.)
Exit 10 (apparently 'melodic metal' now, though they used to do mostly punk covers. But check them out anyway, I went to school with these guys, and they have serious talent. Ask nicely and I can dredge up a batch of their earlier work.)
Static-X (electronicy dance music-y metal.)
The Mad Capsule Markets (To J-rock as heavy metal is to Cliff Richard. Described by my friend as 'hyped up Japanese death metal'.)
Chimaira (Fast, hard, loud, and good, but not very deep. Stress relief, mainly.)
Machine Head (As above, but slower, heavier, and a bit deeper. Kinda generic.)
Lordi (Rubber monster suits. Heavy rock. Eurovision 2006 winners. No more need be said.)
I don't like much in the way of new bands. Quite frankly, I'm not into the 'scene' enough to get hold of new bands, the whole 'nu' movement was frankly pretty bad, and the metalcore stuff coming onto vogue now frankly isn't as good as the classic stuff, IMO. Trivium are good, but they're no Iron Maiden.
So, pre-2000 stuff:
Judas Priest
Fear Factory
Blind Guardian
Rammstein
Queensrÿche
Bon Jovi (Cheesier than a herd of cows, but good)
Rage Against The Machine (Virtually prophetic)
REALLY classic stuff you should check out, to get a sense of history:
Led Zeppelin
Pink Floyd
Deep Purple
Queen
Gary Moore
Dire Straits
The Rolling Stones
GZR (Sabbath with newer metal vocalists)
ZZ Top
Uriah Heep
Jethro Tull