At the age of nineteen, Metcalfe was appointed political assistant to General Lake, who was then conducting the final campaign of the Second Anglo-Maratha War against Yashwantrao Holkar.

[2] In 1808 he was selected by Lord Minto for the responsible post of envoy to the court of Ranjit Singh at Lahore; here, on 25 April 1809, he concluded the important Treaty of Amritsar securing the independence of the Sikh states between the Sutlej and the Jumna.

[2] His first tenure as Resident at Delhi began on 25 February 1811 for the East India Company (from 1813 for the British Government), and in 1819 he received from Lord Hastings the appointment of secretary in the secret and political department.

[9] In 1827 he obtained a seat in the supreme council, and in March 1835, after he had acted as the first governor of the proposed new presidency of Agra, he provisionally succeeded Lord William Bentinck as the Governor-General of Bengal (1835–36).

During his brief tenure of office (it lasted for only one year) he carried out several important measures, including that for the liberation of the press, which, while almost universally popular, complicated his relations with the directors at home to such an extent that he resigned the service of the Company in 1838.

[8] In 1839, Metcalfe accepted an appointment by the Second Melbourne ministry to the governorship of Jamaica, where labour difficulties created by the recent passing of the Slavery Abolition Act called for a high degree of tact and ability.

He nonetheless had to make some concessions to win support, and the most notable of these was persuading the Colonial Office to grant amnesty to the rebels of 1837-38, and to abandon forced anglicization of the French-speaking population.