Always keep your mind open to new ideas! These 10 experiments created some of rock and metal’s most celebrated music, and we salute them today with the 10 Greatest Collaborations in Hard Rock + Metal.

A collaboration is often most successful when unexpected. The worlds of rock and rap haven’t always gotten along, and mixing the two genres has led to some less-than-stellar results in the past. However, a few iconic records have come from this sort of crossover, like Aerosmith and Run-D.M.C.’s version of “Walk This Way.” Even rapper DMC hated the remix for a while, but eventually came around as “Walk This Way” became a legitimate phenomenon.

We couldn’t talk about collaborations without mentioning Queen and David Bowie’s beloved “Under Pressure.” Two of the greatest frontmen in history — Freddie Mercury and David Bowie — wrote the cut with Queen guitarist Brian May and bassist John Deacon back in 1981. Evolving from a simple jam session between the musicians at Queen’s Swiss studio, “Under Pressure” has proven to be timeless and is instantly recognizable by any generation, especially at karaoke bars.

Another brilliant, yet inexplicable collaboration was concocted when The Dillinger Escape Plan brought Faith No More’s Mike Patton into the studio for the Irony is a Dead Scene EP. Still one of the weirdest records ever released, the two entities became brilliantly interwoven for the experiment.

Check out our picks for the 10 Greatest Collaborations in Hard Rock + Metal above!

10 Unforgettable 'Wikipedia: Fact or Fiction?' Moments