Disturbed fans in Nashville Saturday night (May 7) got an unexpected surprise as Halestorm's Lzzy Hale joined David Draiman onstage to sing a duet cover of U2's "I Still Haven't Found What I'm Looking For."

For those who've followed Disturbed on this tour, you've likely seen the band perform the U2 classic as part of a covers medley that includes Nine Inch Nails' "Closer," The Who's "Baba O'Riley" and Rage Against the Machine's "Killing in the Name." But the addition of Hale during the U2 portion, which comes second in the medley, was a welcome surprise. Watch fan-shot video of the performance above.

Hale has a history with Draiman as she collaborated with the singer on a cover of the Lita Ford / Ozzy Osbourne duet "Close My Eyes Forever" for Draiman's other band, Device. Given Hale's Nashville ties, it appeared to be the perfect opportunity for the singer to reconnect with Draiman and treat the audience at Nashville's Ascend Amphitheater to a memorable moment.

Disturbed have a long road ahead of them, with dates in North America and Europe booked through August. Plus they have an Australia / New Zealand run on the books for November. See all of their dates here. As for Hale, she's in the midst of a little breather from the road, but Halestorm will return to touring on May 14 in Cherokee, N.C. They too have shows booked into August. See all of their scheduled dates at this location.

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