What flag inspired the coiled snake image on Metallica's 1991 album cover?

The coiled snake image on Metallica's 1991 album cover was inspired by the Gadsden flag.

The cover of Metallica shows the band's angled logo in the upper left and a coiled snake in the lower right. The snake is derived from the Gadsden flag, an American Revolutionary-era symbol traditionally shown with the motto “Don't Tread on Me.”

That motto also became the title of a song on the album, creating a direct connection between the artwork and the record's track list. The image is subtle because the original cover used nearly black embossed emblems against a black background.

Later editions made the logo and snake easier to see by using dark gray elements. The album's nickname came from this deliberately restrained black presentation rather than from an official title.