O.h.m.
                 O.L.D. (Old Lady Drivers)
                 Oakhelm
                 Oath to Vanquish
                 Oathean
                 Obituary
                 Oblique
                 Obscura
                 Obscurant
                 Obscure Bergen
                 Ocean, The
                 Oceano
                 Octavia Sperati
                 October File
                 Odious Mortem
                 Of Graves and Gods
                 Of Infinity
                 Of Legend
                 Of Sound Mind
                 Ojeda, Eddie
                 Old Dead Tree, The
                 Old Man's Child
                 Omegalord
                 Omnium Gatherum
                 On Broken Wings
                 On Paths of Tornment
                 On The Outside
                 On The Rise
                 One Dead Three Wounded
                 One Man Army And The Undead Quartet
                 One Way Mirror
                 Onesidezero
                 Onslaught
                 Open Hand
                 Open Hand
                 Opeth
                 Opiate For The Masses
                 Opposition Party
                 Opprobrium
                 Opus Dai
                 Orange
                 Orange Goblin
                 Orchid's Curse
                 Orcrist
                 Ordeal, The
                 Order By Chaos
                 Order of Ennead
                 Order Of The Ebon Hand
                 Orgy
                 Origin
                 Orphan
                 Orphanage
                 Orphaned Land
                 Orphans In Coma
                 Orthrelm
                 OSI
                 Osyrus
                 OTEP
                 Outbreak
                 Overcast
                 Overkill
                 Overmars
                 Oxbow
                 Oxiplegatz
                 Ozzy Osbourne