The heavy metal rocker, who is a big fan of Doctor Who, was approached by producers when Slipknot had a tour stop in Cardiff, Wales, where the show is filmed, in January (15) and he was offered a small part.
A spokesperson for the series says, "We asked him if we could record his roar to use for the monster and he was completely up for it!"
Taylor will provide the roar of Fisher King, a green alien creature, in the episode set to air in the U.K. on Saturday (03Oct15).
He shared the news on Twitter.com, writing, "You have NO idea how hard it's been to keep this awesome secret."
The monster is also voiced by actor/comedian Peter Serafinowicz.