Metallica's 1991 album was originally discussed under the working title “Married to Metal.”
The phrase arose from the personal circumstances surrounding the recording sessions. Several members of Metallica were going through divorces while the album was being made, and “Married to Metal” became an informal working idea rather than the final public title.
Other possibilities were considered, including the number “Five,” reflecting the album's position as the band's fifth studio release, and the title of one of the songs. The band eventually chose the simple eponymous title Metallica because it fit the record's direct presentation.
The album became widely known as The Black Album because its original cover used a nearly black background with subtly embossed versions of the Metallica logo and a coiled snake. That nickname is not the official title, but it became so dominant that many listeners use it more often than Metallica.