The Metallica frontman and former Van Halen star Sammy Hagar hosted their second annual Acoustic-4-A-Cure event in San Francisco, and recruited some of their famous friends to perform at the concert.

Hetfield brought out his own surprise guest, 16-year-old daughter Cali Hetfield, as they sang a rendition of Adele's Crazy For You, much to the delight of the crowd. He was later joined by Alice in Chains' Jerry Cantrell to sing Blue Oyster Cult's (Don't Fear) The Reaper.

Among the other unlikely and unexpected duets was comedian Adam Sandler joining forces with Train's Pat Monahan and Red Hot Chili Peppers drummer Chad Smith, as the trio covered Led Zeppelin's Ramble On, and Linda Perry and Chickenfoot's Joe Satriani, who covered Zeppelin's Communication Breakdown.

Hetfield and Hagar's Acoustic-4-A-Cure raises funds and awareness for the Paediatric Cancer Program at the University of California, San Francisco Benioff Children's Hospital.