One of my favorites, I didn't like Lateralus much first... now I can say it's one of the best albums in my collection. Very creative and talented musicians. I would call them "art-rock" or something like that. They're definitely not nu-metal.
Symphony X
Dream Theater
Pain of Salvation
Ark
Fates Warning
Queensrÿche
Shadow Gallery
Rush
Vanden Plas
Evergrey
Tunnelvision
Power of Omens
Iron Maiden
Megadeth
Metallica
Death
Opeth
Dark Tranquillity
Soilwork
Paradise Lost
Control Denied
Katatonia
Arcturus
Tool...