Marsters is best known for his performances as the vampire Spike in Buffy the Vampire Slayer and its spin-off, Angel. Other recurring roles in popular science fiction/fantasy series include the role of Milton Fine/Brainiac in Smallville, as well as Barnabas Greeley in Caprica.
He has also guest starred in Star Wars: The Clone Wars, Numb3rs, and Lie To Me, and his film credits include Dragonball Evolution and P.S. I Love You. In 2011 he once again acted alongside Torchwood star Naoko Mori, in the SYFY TV movie Three Inches.
Besides acting, Marsters is also a musician. Not only is he a singer/songwriter, but also plays the guitar, and has performed both with his band Ghost Of The Robot as well as a solo artist.