Fontana was born in Paris, 20 years to the day after the atomic bombing of Hiroshima, and his choice of the artistic name Megaton was influenced by this.

He grew up in a Paris banlieue, and after qualifying for a diploma in psychology, was active as a graphic artist and also adept in graffiti art.

[1][2][3][4] Fontana first started making shorts and video clips before finally directing feature films.

[9] Aside from filmmaking, Fontana is also a published author after his novel, entitled Le Facteur humain ("The Human Factor"), was released in 1998.

[5] In 2021, Fontana returned to film production to release a Netflix documentary entitled "Monsters Inside: The 24 Faces of Billy Milligan", the documentary received criticism shortly after release for its stigmatism regarding dissociative identity disorder.