He was the lead singer and frontman of the hard rock band UFO, which he co-founded with longtime friends Pete Way, Andy Parker and Mick Bolton in 1968.

[4][5] However, UFO are often cited as one of the key influences on the hard rock and heavy metal scenes of the 1980s and 1990s, including bands such as Metallica, Judas Priest, Iron Maiden, Guns N' Roses, Def Leppard, Slayer, Megadeth, Testament, Overkill, Anthrax, Alice in Chains, Tesla and Dio.

In 1997, during UFO's hiatus, Mogg and Way, under the moniker Mogg/Way, released a couple of albums, Edge of the World and Chocolate Box.

[2] In 2002, he was in a side project, $ign of 4, featuring Cosmosquad members Shane Gaalaas on drums and Jeff Kollman on guitar.

In late 2003, having regained the rights to the UFO name from Schenker, Mogg spoke with Pete Way and Paul Raymond, and ended up having a reunion tour which later brought the band back for good, with newly hired American guitarist Vinnie Moore.