The Huddersfield line is the main railway line between the English cities of Leeds and Manchester, via Huddersfield. It is one of the busiest MetroTrain lines. The route travels south-south-west from Leeds through Dewsbury. After a short westward stretch through Mirfield, where it runs on the ex-L&YR section, it continues south-west through Huddersfield, using the Colne Valley to its headwaters. The long Standedge Tunnel, just after Marsden, crosses under the watershed; the majority of the run down to Manchester is in the Tame Valley. From Manchester, some services continue to Manchester Airport and others to Liverpool.

Metro is the passenger information brand used by the West Yorkshire Combined Authority in England. It was formed on 1 April 1974 as the West Yorkshire Passenger Transport Executive (WYPTE), at the same time as the metropolitan county of West Yorkshire. The Metro brand has been used from the outset and, since the formal abolition of the WYPTE on 1 April 2014, it has remained the brand name of public transport in the region, overseen by the West Yorkshire Combined Authority, which is also responsible for the delivery of transport policies.