Riff lord Tony Iommi has been churning out unforgettable music for over four decades now. You can argue that if it weren't for this Black Sabbath legend, heavy metal music as we know it may not have ever existed. More than 40 years after first gracing the music world with his genius, Iommi is still going strong, as evidenced by Black Sabbath's latest album, the stellar '13.'

Death metal madman Trey Azagthoth has a keen sense for writing riffs that cause tectonic plates to violently collide and upheave the earth. Morbid Angel’s ‘Altars of Madness’ is hailed as one of the all time greatest death metal albums due to Azagthoth’s virtuosity. Azagthoth is also one of the fastest guitarists in history, which can be heard in his chaotic soloing that seems downright inhuman.

Tony Iommi or Trey Azagthoth? Cast your vote for the Greatest Metal Guitarist in the poll below! Voting for this round closes on Sunday, July 21 at 11:59pm ET. Fans can vote once per hour, so keep coming back to make sure that your favorite metal musician wins!