 He represented 
Plympton Erle, Devon from 1790 to 1796 and Malmesbury Wiltshire from 1796.Of his parliamentary career, Metcalfe left few records, each times voting on Pitt side including Richmond's fortifications plan along the southern coast of England (27 Feb 1786) and stood with him on the most debated Regency Bill of 1789.With the financial success brought by the gin trade, Metcalfe became a passionate art collector and was a patron of the Arts, among his friends and acquaintances were the writers Samuel Johnson, Frances Burney, the painter Sir Joshua Reynolds, the philosopher Jeremy Bentham and West India merchant and art collector Robert Fullarton Udny (1722–1802) of Udny Castle in Aberdeenshire, Scotland and later of "Udny House" at Teddington, Middlesex.