He quickly became one of the most successful male singers in France during the era of yé-yé music, touring with Claude François, and had hits from 1964 including "Même si je suis fou", "Un verre de whisky" (based on the Marvin Gaye song "Can I Get a Witness"), and "Ce n'est pas vrai".

Monty often wrote his own lyrics to the tunes of American pop songs, and became a writer of songs for other artists including Éric Charden ("Le monde est gris, le monde est bleu"), Sheila ("Petite fille de français moyen"), France Gall ("Mon p'tit soldat"), and Dalida ("Mama").

In 1966, he replaced Daniel Filipacchi as host of the popular Europe n° 1 radio programme Salut les copains.

In 1976, he found further success writing and producing his song "Allez les verts", created for the supporters of football club AS Saint-Étienne.

He published an autobiography, Ma vie en vert du showbiz au chaudron, in 2017.