[3][6][5] Up to that point, he had been heavily involved in kart racing all over the UK and the Channel Islands, as well as a successful Ginetta Junior racer before moving into single seater categories.

[8] He also competed in the Formula 3 based Euroformula Open championship for Carlin Motorsport, achieving his first single seater race win at the 2019 Pau Grand Prix.

A number of F1 drivers have shown support of Monger, including Jenson Button, Lewis Hamilton, Max Verstappen, Daniel Ricciardo, Jolyon Palmer and Nico Hülkenberg.

[15][16] In June 2017, it was announced that Monger would return to competition in November, sharing a Group CN Ligier JS53 Evo 2-Honda with quadruple amputee Frédéric Sausset in a round of the V de V Challenge Endurance Proto at the Autódromo do Estoril in Portugal, as part of a programme with the eventual aim of fielding a team of three disabled drivers at the 2020 Le Mans 24 Hours.

[20] In order to compete in F3, he and his family had to appeal to the sport's international governing body, the Fédération Internationale de l'Automobile, to change their regulations, as they had restricted disabled drivers from racing single seaters on the grounds of safety: the FIA decided to lift the ban in December 2017, allowing disabled drivers to race appropriately-modified single seaters as long as they could pass safety checks.

[9] In June 2018, Monger drove a Formula 1 racing car for the first time when he tested a Sauber C30 at the Rockingham Motor Speedway in Corby.

In March 2021, Monger completed "Billy's Big Challenge", covering a distance of 140 miles (230 km) by walking, kayaking and cycling, and raised over £3 million for Comic Relief.

[24] A documentary feature about Monger's first Formula 1 drive was shown as part of Sky F1's coverage of the 2018 Austrian Grand Prix.