He was born and raised in Stockholm, where he also made his debut as a soloist. He continued with leading roles at Folkoperan, Wermlandsoperan, Malmö Opera, Gothenburg Opera and the Royal Opera in Stockholm, which he had as his "home stage" between 1996 and 2009. Since then, he has had the majority of his engagements abroad. Among other things, he has sung at the opera houses in Copenhagen, Kiel, Stuttgart, Riga, Dublin, Halle, Manchester, Linz, at the Concertgebouw in Amsterdam, in New Zealand and in Brazil. In 2009 he made his debut at Covent Garden in London where he sang Tristan in Tristan and Isolde opposite Nina Stemme. In 2011 he sang the title role in Wagner's Tannhäuser in Bayreuth and in 2013 he debuted at the Metropolitan Opera in New York as Siegfried, both in Siegfried and Götterdämmerung. In 2016 he toured the UK with Opera North, again as Siegfried in their production of Wagner's Ring to return in 2017 to the Royal Opera House in Stockholm for new acclaimed performances as Siegfried. 2018 included Stenhammar's cantata "Sången" with the Gothenburg Symphony Orchestra with Neeme Järvi, which was also released on CD. In 2019 Lars made Siegmund in Valkyrian at the Teatro Petruzzelli in Bari and in 2020 the Croatian debut came at the Opera in Rijeka as Tristan under the direction of Ville Matvejeff. In 2022, Lars returned to the Teatro Petruzzelli in Bari, this time as Tristan, which he also did again in Rijeka later that year.
Lars has also participated in a number of opera recordings. Among the latter is a live recording from 2013 at the Albert Hall in London where he sings the title role in Parsifal. The recording of Götterdämmerung in which he sings Siegfried, conducted by Sir Mark Elder, received the 2010 Grammophone Award for Best Classical Opera Recording.