Established in 1851, the original Amalgamated Engineering Union was a branch of the British union. It was registered with the Commonwealth Conciliation and Arbitration Court in 1905 and became known as the Amalgamated Society of Engineers. In 1920 it amalgamated with ten other engineering and allied trade unions and changed its name to the Amalgamated Engineering Union, Australian Section in 1921. In 1968 the union became autonomous from its parent body in Britain, shortening its name to the Amalgamated Engineering Union to reflect this. In mid-June 1972 the AEU began a series of amalgamations with the Sheet Metal Workers, Blacksmiths & Boilermakers and Federated Jewellers to form the Amalgamated Metal Workers' Union by 1973.

The Boilermakers' and Blacksmiths' Society of Australia was formed in 1965 when members of the deregistered Blacksmiths' Society of Australia joined the Boilermakers' Society of Australia. In 1973 it joined the Amalgamated Engineering Union and the Sheet Metal Workers to form the Amalgamated Metal Workers' Union.