Two words;

DREAM THEATER

Quick list of stuff and reccomended albums in brackets

Nightwish (any)
Lacuna Coil (Comalies)
Metallica (Kill Em All/Ride The Lightening/Master of Puppets/...And Justice For All/Metallica/Load/ReLoad/Garage Inc/S&M/St Anger)
Megadeth (Countdown To Extinction/Youthanasia/Cryptic Writings/The World Needs A Hero/The System Has Failed)
GnR (Appetite For Destruction/Use Your Illusion 1+2)
Pantera (Cowboys From Hell)


If you want a bit of the 80's rock stuff go for;

Def Leppard
Warrant
Tigertailz
Whitesnake
Quireboys
Motley Crue
Van Halen
RATT
Skid Row
Europe
L.A. Guns
Extreme
Living Color
Steve Vai
Joe Satriani

Classic rock/hard rock

AC/DC
Deep Purple
Led Zeppelin (of course)
Judas Priest
Rainbow
Black Sabbath
Pink Floyd
Aerosmith
YES
Rush
King Crimson
Symphony X
EdGuy
Lynyrd Skynyrd
Motorhead
Anthrax
Kiss

Heavy metal;

Slayer
White Zombie
Meshuggah
At The Gates
Godsmack (very metallica-like, EXCELLENT live band)
Corrosion Of Conformity
Iced Earth
Coal Chamber
Fear Factory
Sunna
Distrubed
Racer X


But seriously, check out DREAM THEATER (and if you can handle even more prog'ness - "Liquid Tension Experiment" are a good band!!!)