The Metropolitan Line grew out of the Metropolitan Railway, one of the earliest Underground railways in the world. It's one of the furthest-reaching London Underground lines, as although its south-east end is just at the edge of the City of London, it extends into rural Buckinghamshire in the north-west. On a standard tube map, the Metropolitan Line is maroon or purple.

                Amersham   Chesham
                      |       |
Uxbridge    Chalfont and Latimer   Watford
  |                   |            /
  |                   \           /
Hillingdon      Chorleywood   Croxley
  |                     \       /
Ickenham       Rickmansworth   /
  |                       \   /
  |                        \ /
Ruislip                     v
  |                         |
  |                     Moor Park
  |                         |
Ruislip Manor           Northwood
  |                         |
Eastcote             Northwood Hills
  |                         /
Rayners Lane             Pinner
  \                       /
   \                 North Harrow
West Harrow            /
      \               /
       Northwick Park
        Preston Road
        Wembley Park
        Finchley Road
        Baker Street
    Great Portland Street
        Euston Square
   King's Cross St Pancras
       Liverpool Street

The Metropolitan Line is concurrent with the Piccadilly Line from Uxbridge to Rayners Lane; with the Jubilee Line from Wembley Park to Baker Street (with fewer stops); with the Circle Line from Baker Street to Aldgate; and with the Hammersmith and City Line from Baker Street to Liverpool Street.

Connections to the Bakerloo Line at Baker Street; to the Northern Line at King's Cross St Pancras and Moorgate; to the Piccadilly Line and Victoria Line at King's Cross St Pancras; and to the Central Line at Liverpool Street.

National Rail connections at Amersham, Chalfont and Latimer, Harrow-on-the-Hill, Euston Square for Euston, King's Cross St Pancras for King's Cross and St Pancras, Farringdon, Barbican, Moorgate and Liverpool Street.
