Interaction of poly(2-vinylpyridine)-poly(ethylene oxide) (P2VP-b-PEO) diblock copolymers with noble metal compounds in aqueous media and metal nanoparticle formation in such systems were studied. In all cases, the characteristics of the micelles filled with metal compounds strongly depend on the nature and geometry of the metal compound, which, in turn, influences the morphology of the finally produced metal nanoparticles. Metal compound addition induces micellization even at very low pH values, where the P2VP-b-PEO block copolymers are dissolved molecularly. The driving force of such a micellization is the coordination of VP units with metal ions, which proceeds by three different basic scenarios, depending on the type of metal compound and the pH of the medium. In all the cases the P2VP-b-PEO micelles containing metal compounds work as "nanoreactors" for metal nanoparticle formation.