Enter Sandman, Metallica’s eponymous1991 album eventually went platinum, and the band became one of the biggest heavy metal acts around. Since then, the influence of “Enter Sandman” has rippled out into the larger culture. Since 1999, Mariano Rivera, surely the greatest relief pitcher in the history of baseball, has ritually made his entrance to the game with “Enter Sandman” providing the soundtrack. (Perhaps a strange pick for a mild-mannered, deeply religious man. But somehow it works.) And the song has been covered umpteen times — by other metal bands (most notably Motörhead) but also by Weird Al Yankovic, Pat Boone, and the bluegrass band called Iron Horse.