Mettenberger originally attended the University of Georgia but was kicked off the team due to a violation of team rules. On April 30, 2010, Mettenberger pled guilty to two sexual battery charges stemming from an incident at a bar near Valdosta, Georgia. He transferred to Butler Community College, where he became the starter. In his lone season at Butler he had 2,678 yards passing yards with 32 touchdowns and four interceptions. Prior to 2011, he transferred to Louisiana State University. In his first season at LSU, he completed eight of 11 passes for 92 yards and a touchdown. In 2012, he took over as the starting quarterback. He led the team to a 10-3 record, completing 58.8% of his passes for 2,609 yards, 12 touchdowns, and 7 interceptions.
In Mettenberger's senior season, he tore his ACL in LSU's final regular season game. He underwent surgery and expects to be ready before the NFL draft.