A composition for the treatment of metal surfaces and for the deposition of metals or metal alloys on plastics surfaces contains a) at least one polymer as component A, composed of the structural element (1) and at least three structural elements selected from the group consisting of b) water or another solvent which is suitable for dissolving, dispersing, suspending or emulsifying the polymer, as component B; c) if required, surface-active compounds, dispersants, suspending media and/or emulsifiers as component C. In a process for the treatment of a metal surface and a process for the deposition of metals or metal alloys on a plastics surface, the metal or plastics surface is brought into contact with a polymer (component A). Furthermore, polymers (component A) are used for the treatment of metal surfaces and for the deposition of metals or metal alloys on a plastics surface, and polymers composed of special components A′a, A′b and A′c.