Metallica‘s Robert Trujillo and Kirk Hammett gave Boston sports fans a treat last night by leading a “Sweet Caroline” sing-along during the band’s Gillette Stadium concert. For over two decades Neil Diamond‘s Top 5 1969 hit has been a fixture at Boston’s Fenway Park, with fans singing along with the song in the middle of the eighth inning of every Red Sox game. You can watch Trujillo and Hammett play and sing “Sweet Caroline” below. “This song is really scary, super heavy and if you start moshing try not to injure yourself, because it’s such a scary song I’m already shaking,” Trujillo joked be…