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.

When their original bassist left Opeth two years later, Åkerfeldt replaced him on bass, and Isberg then assumed guitar duties.

[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."

[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.

[11] He is also presumed to be the basis for the character Toki Wartooth from the popular cartoon Metalocalypse, as revealed in an interview with Ultimate Guitar.