Described is a new process for applying a metal coating to a non-conductive substrate comprising the steps of (a) contacting the substrate with an activator comprising a noble metal/group IVA metal sol to obtain a treated substrate, (b) contacting said treated substrate with a composition comprising a solution of: (i) a Cu(II), Ag, Au or Ni soluble metal salt or mixtures thereof, (ii) 0.05 to 5 mol/I of a group IA metal hydroxide and (iii) a complexing agent for an ion of the metal of said metal salt, wherein an iminosuccinic acid or a derivative thereof is used as said complexing agent.