Metcalf-Lindenburger was selected by NASA in May 2004 as an Astronaut Candidate. Astronaut Candidate Training includes orientation briefings and tours, numerous scientific and technical briefings, intensive instruction in Shuttle and International Space Station systems, physiological training, T-38 flight training, and water and wilderness survival training. Successful completion of this training in February 2006 qualified her as a NASA Astronaut. She served as a Mission Specialist on STS-131, an April 2010 Space Shuttle mission to the International Space Station. The mission's primary payload was the Multi-Purpose Logistics Module.