Oak, Ash & Thorn (Pagan/Folk-metal)
‡ Oakenshield (Viking/Folk-metal)
‡ Oakhelm (Pagan Folk Black Metal)
Oak Pantheon (Folk/Pagan/Black Metal)
‡ Oak Roots (Folk-metal)
Obereg (Folk/Pagan Metal)
Obscurity (Pagan/Viking Metal)
‡ Ocelon (Celtic Folk-metal)
‡ ODR (Folk-metal)
Odraedir (Pagan/Folk-metal)
Odroerir (Folk-metal)
‡ Ofärd (Folk-metal)
‡ Ogmiös (Folk-metal)
O’Hamsters (Celtic Punk)
‡ Ol’ Jolly Roger (Pirate Metal)
‡ Omiors (Occitan metal)
‡ Omut (Folk-metal)
‡ Onkel Hryum (Trash/Death/Folk-metal)
‡ Open Access (Folk-metal)
‡ OracleVuh (Folk-metal)
Oprich (Folk-metal)
Orphaned Land (Folk-metal)
Oscenrad (Anglo-Saxon Heathen Metal)
‡ Oskord (Folk-metal)
‡ Othalan (Folk-metal)
‡ Otyg (Folk-metal)