Disturbed continue to have a blast on tour and their rock medley is proving to be quite the popular addition to the set. Not only do the band cover songs from Nine Inch Nails, U2, The Who and Rage Against the Machine in succession, but it's also offered the band the chance to welcome some of their friends in other acts to the stage for surprise collaborations. The latest instance happened over the weekend while Disturbed were rocking the Rocklahoma Festival.

Sixx: A.M. vocalist James Michael got first crack, walking out onstage during the U2 portion of the medley, trading lines with David Draiman on the anthemic classic "I Still Haven't Found What I'm Looking For."

As Michael exited the stage, his Sixx: A.M. bandmate Nikki Sixx replaced him, joining Disturbed for The Who portion of the medley. The bassist was frequently spotted hanging alongside bassist John Moyer as the double basses lent even more low end to "Baba O'Riley." Sixx fist bumped with Dan Donegan and Moyer, before giving a hug to Draiman and exiting the stage. Footage of both Michael and Sixx joining Disturbed onstage for the respective songs in the medley can be seen in the player above.

Disturbed previously welcomed such guests as Jacoby Shaddix from Papa Roach and Lzzy Hale from Halestorm during their rock medley. Shaddix took on the Rage Against the Machine "Killing in the Name" portion, while Hale traded vocals with Draiman on U2's "I Still Haven't Found What I'm Looking For" at a past show.

Both Disturbed and Sixx: A.M. have a wealth of touring ahead of them in 2016. Disturbed are promoting their Immortalized album and currently have dates booked around the world through November. See their tour itinerary here. Sixx: A.M. recent released the first volume of the two volume Prayers for the Damned. Like Disturbed, they too have a world tour in motion with shows booked into November. See their dates here.

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