The National Union of Lock and Metal Workers (NULM) was a trade union representing workers involved in the manufacture of metal items in the United Kingdom. The union was founded in 1889 in Willenhall as the National Amalgamated Lock, Latch and Key Smiths' Trade Society, soon renaming itself as the National Amalgamated Lock Maker and Metal Workers' Trade Society to better reflect its membership, which peaked at 2,000 in 1900, falling back to only 180 ten years later.