What working title did Metallica use for The Black Album during its development?

Metallica's working title for The Black Album was Married to Metal.

The phrase arose as a running joke during a turbulent period for the band. Kirk Hammett, Lars Ulrich, and Jason Newsted were divorcing their wives during the album's production, and the title humorously connected their personal circumstances with their intense commitment to the band.

The title was never intended to become the final name. Other possibilities reportedly included Five and the title of one of the songs. In the end, Metallica chose the simple eponymous title Metallica because the members wanted to keep the presentation straightforward.

The nickname The Black Album developed from the artwork rather than from the original working title. The first edition used a nearly black cover with subtly embossed versions of the band's logo and a coiled snake, making the informal name more memorable than the official title.