Where to begin ...
Black Sabbath, Anthrax, Alice In Chains, Aborted, American Head Charge, Carcass, Children of Bodom, Chimaira (new album is immense!), Chokehold, Crowbar, Corrosion of Conformity, Celtic Frost, Cathedral, Cryptopsy, Down, DevilDriver, Devin Townsend Band, Dragonforce, Dream Theater, Drowning Pool, Ektomorf, Exodus, Fear Factory, God Forbid, hatebreed, Henry Rollins, In Flames, Illdisposed, Iron Maiden, Judas Priest, Killswitch Engage, Korn, Kreator, Krisiun, Lamb of God, Limp Bizkit, Led Zeppelin, Lynyrd Skynyrd, Machine Head (New album = godly), Meshuggah, Metallica, Megadeth, Motorhead, Method of Destruction, Mudvayne, Mushroomhead, Napalm Death, Nevermore, Nile, Nocturnal Rites, Opeth, Ozzy Osbourne, Old Mans Child, Obituary, Pantera, Panic Cell, Primus, Prodigy, Probot, QOTSA, Quo Vadis, Rammstein, Rage against the Machine, Run DMC, Seether, Satyricon, Sepultura (Max Cavalera-era only; can't get into the new stuff), Slipknot, Slayer, Shadows Fall, Sikth, Soil, Skinlab, Soilwork, Soulfly, Spineshank, Static X, Stone Sour, Strapping Young Lad, Superjoint Ritual, System of A Down, Tool, Threat Signal, Thin Lizzy, Type O Negative, Unleashed, Unforgiven Kingdom, Vader, War, Xzibit, Yes.
About 75% of my album collection I reckon. And yes, these are my favourite bands; if they're not listed, they're not my favourite. ;-)