O'May was born in Rouen, France. As a teenager, he was a fan of rock music and R&B from the Osmond Brothers, but the album Machine Head by Deep Purple inspired him to become a hard rock guitarist. He joined the heavy metal band Marienthal about 1982. He gave guitar lessons and took himself from Patrick Duplan which made him explore classical music, blues, and bossa nova.[where?] Marienthal toured France, England, and Algeria, and opened for acts such as Girlschool, Alvin Lee, and Chariot. After conflicts with their manager, the band split in 1987. O'May continues touring with the group Road 66 across France but playing in bars led to excesses. O'May decides to put an end to this drift during a tour in Belfort He stayed in Belfort where he met the band Ange well as drummer Peter Hartmann and bassist Alain De Bernardi whom he refounded the second group Road 66. They turned in eastern France and Germany.
O'May moved to Brittany in 1989. After a third group experience with Road 66 and the sound of Bretons concerts and bals, he released his first solo album, Bob Up, in 1994, with Bretons renowned musicians (Alain Genty, Michel Aumont, Fred Guichen, Stéphane De Vito). Godin, a French guitar distributor, chose him as its spokesperson. In 1995, he was invited by the Festival "Cannes Passion Music" in Cannes for master classes. This allows him to meet musicians and even play with the rhythm section of Joe Satriani in a closing concert (Stuart Hamm, Rudy Roberts, Jonathan Mover). In 1996, he developed his universe with the album Kids & the War, wherein he joined Celtic instruments (Scottish Snare drum, uilleann pipes).
He recorded his third album, Breizh - Amerika, where refined his ideas of fusing rock and with traditional sounds, adding Celtic music, and involving French guitarist Norbert Krief. He had the album mixed by Guns N' Roses guitarist Ron Thal in New York City, and released it in 1999.
In 2002, O'May produced the album Un Souffle Pour la Vie (Breath for Life) with many artists. He donated the profits to cystic fibrosis research. That year, he also released his fourth album, Anakoustik, and followed with a tour with pianist Philippe Turbin. In 2003, he created a show with the famous Breton singer Gilles Servat for outstanding performance wherein the two artists share their respective directories. At various concerts, he met with many musicians, including Jeff Beck, Joe Satriani, Steve Vai, Van Wilks, Stuart Hamm.
O'May has composed over 100 tracks for the TV serial European coast seen from the sky, which has been distributed to 15 countries. Breton musician Alan Stivell had him play on his album Explore, which released in 2006. O'May also participated in "Brittany celebrates St. Patrick's day" at Paris-Bercy, and played as a guest musician on Johnny Hallyday's "Flashback Tour". In 2007, he signed with Milan Music/Universal label for his fifth studio album, Omega. It was released on 8 July, and he played at the "Festival des Terre Neuvas" in France in front of 47,000 people. In 2008, O'May toured in France and Europe.
Alan Simon invited O'May to participate in the rock opera Anne de Bretagne, which involved musicians Barclay James Harvest, Ange, Fairport Convention, Tri Yann, and Cécile Corbel. O'May also participated in Simon's second project, Excalibur, which is a Celtic rock opera involving musicians such as Alan Parsons, Martin Barre (Jethro Tull), John Helliwell (Supertramp) and Fairport Convention. Excalibur toured in Germany and Switzerland in 2010.
O'May released his sixth album, In Live We Trust, with ten original tracks and a horn section. His concert producer describes his style as "exploring new territory with an original blend of his own well-known guitar approach and world music elements using among others Celtic, Arabian and Chinese sounds". He participated in the 2010 Bercy for St Patrick's Day, and recorded for Excalibur III, which was the third album from the Excalibur rock opera. He continued touring for both of Simon's projects through 2011 and 2012, visiting Switzerland, France, and Germany. He developed a friendship with Martin Barre, and later toured with him in October 2011. In 2012, Martin Barre invited him to join his new group with prestigious line up for several tours in Britain, Germany, Italy, USA. O'May appeared in 2012 as guest on Alan Stivell concerts, in earlier parts of several concerts of Uli Jon Roth (ex-Scorpions guitarist) and played in Nancy Zénith including Scorpions, Pat McManus, Gamma Ray, Karelia and Koritni.
O'May released his seventh album, Celtic Wings, drawing for writing it in his musical (metal), genetic (Ireland) and emotional (Brittany) roots. It gives rise to a Celtic rock and metal album, between new compositions and covers (Alan Stivell medley, Over the Hills and Far Away, Whiskey in the Jar), with the participation of Martin Barre, Alan Stivell, Jonathan Noyce (Gary Moore, Archive), Moya Brennan (Clannad), James Wood, Christophe Peloil (Tri Yann). The album, which he began writing six months before the release in November, is recorded in Britain, Ireland, England and mastered at the famous Abbey Road Studios in London.