Some metal I really enjoy:
-Judas Priest, heavier stuff like Painkiller
-The Devil Wears Prada, a lesser-known band that is simply amazing.
-Parkway Drive, fairly public but still incredible
-Valiant In Fight, a local band from my high-school.
-System of A Down
-Slipknot, I know they seem to have sold out but they still know how to rock out.

-All That Remains
-Bleed the Dream
-Lamb of God
-Amon Amarth
-Slayer
-As I Lay Dying
-Staind(they have a few really really good songs)
-Nickleback, bear with me on this one...Most of it's cheesy/corny. But they have a few songs that are easily classified as metal or hard rock. Examples: Figured You Out and Because of You.
-Way too many to list right now...I could go on for hours on end just because there are so many great bands out there.
You gotta check out this vid:
YouTube - 9 year old guitar prodigy YUTO MIYAZAWA performs Ozzy Osbourne's Crazy Train on Ellen Degeneres