Lewandowski has long been linked with a move to Real Madrid, and it has been suggested that the Spanish giants will launch a big-money offer for the 29-year-old in this summer's transfer window.
Metzelder, however, has branded the Poland international "irreplaceable for Bayern", and has ruled out the German champions selling the forward at the end of the 2017-18 campaign.
"These are old rumours and while I know that Madrid is a dream club for anyone, Bayern will now allow him to leave," Metzelder told Sky Sports News. "Lewandowski is irreplaceable for Bayern, they will not be able to find an alternative for him in the market and as such will not sanction his exit.
"Bayern do not give up their top players, [Toni] Kroos was the only mistake, and they do not need any more money from sales. His change in agent? It doesn't matter, Bayern hold the power and he is under contract, so it will not happen."
Lewandowski has scored 139 times in 181 appearances for Bayern in all competitions.