Green’s Dictionary of Slang

1. the Metropolitan Music Hall, London.

1884		Sporting Times 8 Nov. 2/1: At no other hall known to me do they [...] lay down red cloth as it is done in the case of the Met.
1885		Bulletin (Sydney) 8 Aug. 9/2: We saw this young lady some years ago at the ‘Met.’ where her song-and-dance constituted a considerable attraction.
1908		Sporting Times 4 Apr. 4/3: The ‘Met.’ is one of the oldest of the London halls, dating from last century’s ‘early sixties’; and it has had a uniformly successful career.
1914		E. Wittmann ‘Clipped Words’ in DN IV:ii 133: The Met, the Metropolitan Music-hall.

2. the Metropolitan Railway, part of the London Underground system.

1937

‘C. McCabe’ Face on Cutting-Room Floor 18: Then I was suddenly in the crowd of clerks and typists rushing towards King’s Cross Met station [OED].

3. (US, also Mett) the Metropolitan Opera House, New York; also attrib.

1915		R. Bolwell ‘College Sl. Words And Phrases’ in DN IV:iii 236: mett. Metropolitan (Grand Opera House).
1937		J.M. Cain Serenade (1985) 182: He may want you to sing at the Met.
1951		Green & Laurie Show Biz from Vaude to Video 172: Caruso spared the Met any such embarrassing predicament.
1958		J. Blake letter 21 Aug. in Joint (1972) 120: New boy has also worked as a singer in the met chorus.
1960		(con. 1930s) R. Barber Night They Raided Minsky’s (1968) 307: The Met deal was not mere fancy.

4. (also Mets) the Metropolitan Police, serving London.

1944		‘D. Hume’ Toast to Corpse 91: You haven’t had thirty years in the Mets for nothing, and you’ve been about a bit [OED].
1970		‘Metropolitan Police Sl.’ in P. Laurie Scotland Yard (1972) 325: met, the: the Metropolitan Police – as opposed to other forces.
1974		A. Pierrepoint Executioner 153: [H]e introduced me to a young CID officer in the Mets.
1986		F. Taylor Auf Wiedersehen Pet Two 78: It’s plainclothes from the Met. Asking about you and the deal on the house.
1997		(con. 1960s) A. Frewin London Blues 212: I do not know where ‘here’ is [...] I suspect it is in London. The Met coppers were hardly likely to take me anywhere else.
2000		J.J. Connolly Layer Cake 72: The old bill round there are, compared to the Met, a bit of a joke, carrot crunchers.

5. the Meteorological Office, responsible for weather forecasting; usu. as the Met Office; thus Met man, a weather forecaster.

1946		G. Gibson Enemy Coast Ahead (1955) 214: The met. man says the weather will be clear all the way.
1968		S. Gore Holy Smoke 42: Not even the Chaldeans – who was sorta court stargazers, like our Met Office – could give him the dinkum oil about ’em.