The National Society of Metal Mechanics (NSMM) was a trade union in the United Kingdom which existed between 1872 and 1985.

Led for many years by William John Davis, it was soon renamed the National Society of Amalgamated Brassworkers.

[3] In 1919, members rejected a proposal to join the Amalgamated Society of Engineers, and instead chose to expand the union's remit, renaming the body as the National Society of Brass and Metal Mechanics.

[4] By 1920, it had 37,363 members, but it suffered during the Great Depression, and this figure fell to 15,000 by 1937.

[5] In 1985, the union merged with the Technical, Administrative and Supervisory Section; at this point, its membership was 27,000.