Ljungberg was one of the most successful Swedish wrestlers ever. He won World Championship gold medals in 1993 and 1995, European Championship gold medals in 1995 and 1999, and an Olympic gold medal in 2000.
On November 17, 2004, while receiving care for depression at the psychiatric ward of the Mölndalhospital outside Gothenburg, he committed suicide by hanging himself. His brother reported in interviews afterwards that Mikael was a sensitive person who took setbacks seriously. Also, it was reported that his life after his professional career came to an end had been difficult for him; his mother had died in 2002, the same year as he went through a divorce.
Just before his death he was appointed manager of the sport section for the Swedish Wrestling Federation, an office he would have entered on January 1, 2005.