A former vocalist for the death metal supergroup Bloodbath, he was also the guitarist for the "one-off" band Steel, and a member of the collaboration Storm Corrosion with Steven Wilson.

Åkerfeldt performed the death vocals on Katatonia's album Brave Murder Day and their EP Sounds of Decay.

[8] In 2020, Åkerfeldt was approached by director Jonas Åkerlund to compose the soundtrack for the Swedish six-part Netflix series Clark, which was released in May 2022.

[10][11] He also draws influence from these obscure bands, making references to them in Opeth album titles such as Blackwater Park, Still Life, and My Arms, Your Hearse, as well as in songs like "Master's Apprentices" and "Goblin."

He is also heavily influenced by jazz, the musician Ritchie Blackmore,[2] Magma and its founder Christian Vander,[12] and Hideki Ishima.

[13] When asked about the album that "made him a metalhead," Åkerfeldt answered that it was probably The Number of the Beast by Iron Maiden, but he also mentioned Lick It Up by Kiss.

[19] Åkerfeldt is known to be friends with Steven Wilson, the frontman of one of his favorite bands, Porcupine Tree, who also produced the Opeth albums Blackwater Park, Deliverance, and Damnation; Mike Portnoy, drummer of Dream Theater (who is featured in their music video for "Wither"); and Jonas Renkse of Katatonia.