100 Demons
108
Obituary
Oblige
Obscura
Oceano
Oceansize
Of Buried Hopes
Of Hearts And Shadows
Oh, Sleeper
Old Man Gloom
Old Mans Child
Omni
On A Pale Horse
On Broken Wings
On The Last Day
Once Nothing
One Dead Three Wounded
One Dying Wish
One Flew West
One Man Army And The Undead Quartet
One-way Mirror
Onelinedrawing
OneRepublic
Onesidezero
Open Hand
Operation Ivy
Opeth
Opiate For The Masses
OPM
Orchid Ablaze
Order Of Ennead
Orgy
Origin
Orphaned Land
Orwell
Otep
Our Lady of Bloodshed
Our Lady Peace
Our People Versus Yours
Ov Hell
Overcast
Overkill
Ozzy Osbourne
The Ocean