[lol]

Here are some I've heard of, in alphabetical order (don't like most of them though):
These are mostly black/doom/death metal, some are power metal, but I guess they are pretty Gothic.

Adorned Blood
At The Gates
Arcana
Behemoth
Black Label Society
Carcass
Candlemass
Cannibal Corpse
Cryptopsy
Deicide
Death
Dimmu Borgir
Disarmonia Mundi
Dying Fetus
Dream Evil
Disembowelment
Ensiferum
Enslaved
Godflesh
Gorgoroth
Helloween
Into Eternity
Municipal Waste
Napalm Death
Ripping Corpse
Scar Symmetry
Shadows Fall - More metalcore but still pretty dark
Six Feet Under
Sonic Syndicate
Vinterland
Whitechapel - More metalcore aswell, but still dark