Educated at Malvern Wells, Eton College and the Royal Military College, Sandhurst,[1] Metcalfe was commissioned into the Rifle Brigade as a lieutenant in September 1874.

[2][3] He served as Commanding Officer of 2nd Battalion of the Rifle Brigade during the Second Boer War, taking part in the Relief of Ladysmith, and was promoted to colonel on 29 November 1900.

For his service in the war, he was appointed a Companion of the Order of the Bath (CB) in the October 1902 South African honours list.

[4] He stayed in South Africa until after the war had ended in June 1902, and received the substantive rank of colonel on 7 November 1902, when he was appointed colonel on the Staff commanding the Troops in British Mauritius with the local rank of Brigadier-General.

[5][2] The Mauritius command had been vacant since the start of the war in late 1899.