Joachim Low's men slipped to a 1-0 defeat at the hands of Spain in the European Championship final on Sunday, a disappointing conclusion to a record-breaking sixth appearance in the tournament's showpiece occasion.
"We had to fight very hard to reach this final. I think we have much more quality to show and we have to improve as a team.
"We now have two years to qualify for the World Cup and try to reach the final again."
Metzelder's defensive partner, Per Mertesacker, agrees with his colleague.
"There are lots of emotions going through my head that you can't describe, for example the fantastic German fans, who were always behind us even after the Croatia defeat," he said.
"We hope that we can improve from these games and learn from them. We are still a young side and a good squad that wants to improve.
"We have reached a point where you can say 'it's not the end'."