"Enter Sandman" is a song by American heavy metal band Metallica. It was released as the first single from their eponymous fifth album, Metallica in 1991. The music was written by Kirk Hammett, James Hetfield and Lars Ulrich. Vocalist and rhythm guitarist Hetfield wrote the lyrics, which deal with the concept of a child's nightmares. The single achieved platinum certification for more than 1,000,000 copies shipped in the United States, spurring sales of over 30 million copies for Metallica and propelling Metallica to worldwide popularity. Acclaimed by critics, the song is featured in all of Metallica's live albums and DVDs released after 1991 and has been played live at award ceremonies and benefit concerts. It is among Metallica's most-played songs, having been performed live by the band 1,133 times.