Bands like Slayer, The Crown, Cannibal Corpse etc aren´t as heavy as they are brutal. I think heavy music is slow, like Black Sabbath, Candlemass, Neurosis, My Dying Bride etc.
Marduk - Panzer Division
Nile - Black Seeds of Vengeance
Dark Funeral - Diabolis Interium
Naglfar - Diabolical
Stone to Flesh - Some Wounds Bleed Forever
Satyricon - Dark Medieval Times
Opera IX - The Call of the Wood
Triumphator - Wings of Antichrist
Krieg - Rise of the Imperial Hordes