Could Metallica be preparing a surprise performance at Yankee Stadium in New York to honor retiring Yankees pitcher Mariano Rivera? That's the rumor reported by the New York Daily News on Monday (August 26th), with the paper noting that Metallica will be in town to perform at the Apollo Theater on September 21st, one day before the Yankees stage a celebration of Rivera's career on September 22nd prior to their game against the San Francisco Giants -- who happen to be Metallica's hometown team. And why would Metallica pay tribute to the legendary Rivera, who's calling it quits after nearly 20 years with the Yanks? Because for most of those years, the future Baseball Hall of Famer has been coming out of the bullpen to close out games to the tune of Metallica's "Enter Sandman" playing on the stadium's P.A. system.