Before becoming a member of HammerFall, he was the guitarist in the band Highlander. Elmgren has also worked with his solo project Full Strike and released one album called "We Will Rise" which was released in 2002. Stefan also plays the guitar in Joacim Cans' solo project Cans.
He quit the band in 2008 to put more energy into his career as a pilot. Currently plays with Full Force.