Enter Sandman was released in 1991 as the lead single from Metallica's self-titled Black Album, written by James Hetfield, Lars Ulrich and Kirk Hammett, whose main riff became one of metal's most famous. The song's nursery rhyme inspired lyrics and menacing build helped it cross from metal radio to sports arenas, wrestling entrances and films. Online, short clips of the riff, often misspelled as Zandman Metallika, circulate on soundboards for instant recognition, borrowed by creators who want a serious entrance without using the full track.