Metallica recently played Genting Arena in Birmingham, England, which is also the hometown of a very little-known heavy metal band called Black Sabbath. While Metallica's James Hetfield and Lars Ulrich were doing whatever they were doing, Kirk Hammett and Robert Trujillo treated the crowd to a little singalong of Sabbath's "War Pigs."
Now if we could just get them to do this more often with the full band, and maybe even keep Trujillo on vocals… might we even suggest the name Sabbitallica?