It is the opening track and lead single from their self-titled fifth album, released in 1991. The music was written by Kirk Hammett, James Hetfield and Lars Ulrich. Vocalist and guitarist Hetfield wrote the lyrics, which deal with the concept of a child's nightmares.
The song is about "nightmares and all that come with them", according to Chris True of AllMusic.[13] The title is a reference to the sandman, a character from Western folklore who makes children sleep.