The first order for electric units for the Metropolitan Railway was placed with Metropolitan Amalgamated in 1902 for 50 trailers and 20 motor cars, which were intended to run as ten 7-car trains, although due to problems with platform lengths these ran as 6-car trains. They were open saloon cars with access at the ends via open lattice gates.

The units had two motor cars which were equipped with Westinghouse electric equipment and four 150 hp motors and ran off-peak as 3-car units with a motor car and a driving trailer. Twenty 6-cars trains were ordered for the Hammersmith & City line that the Met jointly operated with the Great Western Railway with Thomson-Houston equipment and GE76 150 hp motors. In 1904 an order was placed for a further 36 motor cars and 62 trailers with an option for a further 20 motor cars and 40 trailers.

The first electric multiple units ran on 1 January 1905 from Uxbridge to Baker Street, the Uxbridge branch having opened in July 1904 and worked by steam for six months. After problems with the Metropolitan shoe gear on the District Railway were solved, the inner circle began a full electric service on 24 September 1905, reducing the travel time from seventy to fifty minutes.

The trains had first- and third-class accommodation with electric lighting and heating. However, it was quickly found that the lattice gates left the coach ends exposed when working in the open and the cars were modified with vestibules from 1906. Having access only from the end of the coaches was a problem on the busy circle line and centre sliding doors were added from 1911. In 1910 two motor cars were modified with driving cabs at both ends and started work on the Uxbridge shuttle service, before being transferred to the Addison Road shuttle in 1918.