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Foo Fighters

Foo Fighters and Guns N' Roses stunned fans with an epic surprise performance on Thursday.

Midway through their headline set at the Firenze Rocks Festival in Florence, Italy on Thursday, Foo Fighters frontman Dave Grohl invited Axl Rose, Slash and Duff McKagan onstage to perform It's So Easy, from the Guns N' Roses classic album Appetite for Destruction.

Footage of the collaboration shows Rose and Grohl sharing vocal duties, while guitarists Slash and McKagan are seen jamming with the rest of the band.

Rose rocked his iconic red bandana as he raced round the stage in a frenzied and energetic performance as the crowd went wild.

After the Guns N' Roses trio left the stage, the Foo Fighters continued with their hit-laden set, which included Learn to Fly, My Hero, Everlong and a cover of Queen's hit Under Pressure.

Guns N' Roses, who are in the midst of their Not in This Lifetime... Tour, are set to headline Firenze Rocks Festival on Friday.

This isn't the first time the rock bands have collaborated. Last year, Grohl performed Paradise City with Guns N' Roses during the band's tour stop in Tulsa, Oklahoma.

The duet came after the 49-year-old rocker lent Rose his custom-built throne so that he could perform the first date of the band's tour with a broken leg. The throne was first used by Grohl after he broke his leg during a show in Sweden, forcing the band to cancel their headline set at Glastonbury festival.

Rose reportedly said during the show: "I wanna thank Dave Grohl for this; it was very nice of him. I've got nothing to do with this."