The instrumental introduction to Metallica's “Don't Tread on Me” uses a phrase from “America.”
“America” was composed by Leonard Bernstein for the musical West Side Story. Metallica's song incorporates an eight-bar phrase from that melody at its opening before moving into the band's own moderate-tempo heavy-metal arrangement.
The musical reference fits the song's broader imagery. “Don't Tread on Me” connects to the American Revolutionary War, and its title is the motto printed on the Gadsden flag. The same flag's snake inspired the snake shown on The Black Album's cover.
The song was issued to rock radio as a promotional release after the album appeared, but it was not one of the five commercial singles. That distinction is why it is often discussed separately from the album's main single campaign.