Jack Black's taking the stage as "Jack Sabbath" at Tom Morello's festival, which is either the most brilliant bit of rock theatre you'll see all year or a sign that everyone's having a good laugh together, and honestly we're here for both. Getting the Tenacious D frontman involved with the offspring of two metal legends suggests this festival's going to be less stuffy tribute act and more chaotic jam session, which is exactly the kind of energy we reckon could actually make metal fun for people who thought they'd outgrown it. If nothing else, it's the sort of cross-generational rock nonsense that reminds you why live music still matters.