Well... In Sweden, most people basically have two first names (förnamn), where one of the names is the name you use to address the person (tilltalsnamn). That name can be either the first or the second of the first names. Your parents decide which one is the "tilltalsnamn" when you get registered after your birth. It can be changed later if you wish though.
So he actually has both Lars and Mikael as his first names, but Mikael is his "tilltalsnamn"; the name he uses. Did that make it less confusing?