Those inhabiting the worlds of rock and metal have never been shy of a good collaboration. From the sublime to the downright ridiculous (Ozzy and Miss Piggy, we're looking at you), a well-timed, well-placed collaboration can be enough to revive even the most waning of careers, or to open up an artist to a whole new generation of music-hungry fans.
Here, we chronicle 30 of rock's very best collaborations.
