King remembers being called inside by his mother to watch David Bowie perform "Starman" on television, which he cites as one of many influences along with Luke Kelly, Joe Strummer, Johnny Cash, and Freddie Mercury to name a few.

He left Dublin in his twenties, residing in London where he first joined Fastway and later Los Angeles where he formed Flogging Molly with Ted Hutt, Jeff Peters, and Bridget Regan.

[1] King's professional career began in the early 1980s when he was hired as the vocalist for Fastway, a British hard rock band formed by ex-Motörhead guitarist "Fast" Eddie Clarke and ex-UFO bassist Pete Way in 1983.

[2] After Fastway, King formed Katmandu with Mandy Meyer (ex-Krokus) and Mike Alonso (former member of the Detroit-based band Speedball), who released one self-titled album.

[7] On February 5, 2025, the band announced the cancellation of their ongoing tour due to King suffering from a 'very serious health condition.