What flag inspired the snake image on Metallica's The Black Album cover?

The snake image on Metallica's The Black Album cover was inspired by the Gadsden flag.

The cover places a coiled snake in the lower-right area beneath the band's angled logo. The Gadsden flag is historically associated with a rattlesnake and the motto “Don't Tread on Me,” which also became the title of a song on the album.

On the original release, the logo and snake were embossed so subtly against the black background that they were difficult to see. That restrained design helped create the nickname The Black Album, even though the official title is simply Metallica.

The cover is sometimes linked to Spinal Tap's fictional black album, Smell the Glove, because Metallica jokingly acknowledged the resemblance in A Year and a Half in the Life of Metallica. However, the snake motif itself derives from the Gadsden flag.