Metzelder, who used to play for Schalke's arch-rivals Borussia Dortmund, has signed a three-year contract with the Royal Blues, whom he has joined on a free transfer, but his arrival has not gone down well with large sections of the Schalke faithful.
They have not forgiven him for selling t-shirts via his own website ridiculing the Royal Blues when they narrowly missed out on the league titles in 2001 and 2007, and the verdict is still out on whether he will be accepted in Gelsenkirchen.
But Magath has called for the fans to back Metzelder, 29, and help him feel at home for the good of the club.
"I beg you to give him a chance, even if he did not behave particularly correctly once a few years ago," Magath urged club members at their annual general meeting this week.
"Together with us, he has the same aim of finishing the season above our neighbours.
"I am glad that we were able to sign him."
In an interview with the Suddeutsche Zeitung newspaper, Metzelder has justified his transfer to Schalke, saying it is the right step to make after three years largely spent on the sidelines with Real Madrid.
"After my experience in Madrid, where I had hardly any value as a player, it was important for me to join a club who wanted me 100%," he said.
"I have been in contact with Felix Magath for the last two years and he really wanted me, and that was decisive."