Corrosion of Conformity are in the midst of a North American tour which stopped down at Oakland's Fox Theater Sunday night (May 29) and when they did, a very special guest joined in on the fun. The band welcomed Metallica's James Hetfield to the stage to the applause of the crowd.

Hetfield sat in on the performance of the song "Seven Days," adding backing vocals and kicking it at the side of the stage for a majority of the performance. There was no denying Hetfield's powerful belting coming in behind Pepper Keenan's vocals on the track and toward the end of the song, he joined the entire band toward the middle of the stage as they jammed out the closing moments. Check out a photo Corrosion of Conformity posted to their social media below.

The Metallica frontman has a history with Corrosion of Conformity having appeared on their song "Man or Ash," and welcoming Pepper Keenan to appear on Metallica's cover of Lynyrd Skynyrd's "Tuesday's Gone" on their Garage, Inc. EP.

Corrosion of Conformity are in the midst of a North American tour that wraps on June 10 in Fort Wayne, Ind. Beyond that, there are a few scattered dates throughout the summer. See their full itinerary here.

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