He is best known for the 117 songs he has written for the national selections of 12 countries for the Eurovision Song Contest: 74 for Sweden, 16 for Spain, six for Norway, five for Denmark and Finland, three for Georgia, two each for Poland and Malta, and one each for Cyprus, Latvia, Romania, Belgium, Lithuania, Luxembourg and Armenia.

In 2012, G:son achieved his first victory as a winning composer at the Eurovision Song Contest with "Euphoria", performed by Loreen.

In addition to writing and composing songs in various genres for a living, he is the guitarist of the hard rock band Masquerade.

G:son and Henrik Sethsson's song for the Eurovision Song Contest 2001, "Listen to Your Heartbeat", was accused of plagiarism from Belgium's 1996 entry "Liefde is een kaartspel".

The songwriters denied the accusation, but after the Belgian songwriters and the author's organisation SABAM pressed for legal action, a cash settlement was agreed.