"I am thankful for the 13 years. I turned professional straight out of high school and looking back I could not have hoped for a better run," Metzelder told reporters on Thursday. "Even the injuries are part of the story."
The 32-year-old, who won 47 caps for Germany and played in two World Cups including their losing 2002 final against Brazil, had spent seven years at Dortmund before joining Real Madrid for three years until 2010.
Metzelder, who won league medals in both Germany and Spain and also won the German Cup with Schalke 04, returned to the club of his youth but a string of injuries prevented him from holding down a regular starting spot in the last three seasons.
The rugged defender, who also won a third spot with Germany at the 2006 World Cup, won his last cap in their 1-0 Euro 2008 final defeat to Spain.