A process for coating plastic with metals, comprising the steps of a) pretreating the plastic with a composition C comprising at least two different ionic liquids IL1 and IL2, the first ionic liquid IL1 comprising, as cation, at least one alkylammonium cation and the second ionic liquid IL2 comprising, as cation, at least one aromatic heterocycle having a delocalized cationic charge and comprising at least one nitrogen atom; b) treating the plastic from step a) with an activator composition A comprising at least one ionogenic and/or colloidal activator; c) treating the plastic from step b) with an accelerator composition B comprising an acid and/or a reducing agent; d) chemically depositing a metal layer, by treating the plastic from step c) with a coating composition M1 comprising at least one metal salt and at least one reducing agent; e) electrochemically coating the plastic from step d) with at least one further metal layer, by electrochemically treating the plastic from step d) with at least one coating composition M' comprising at least one metal compound, wherein the at least one ionic liquid IL1 comprises an alkylammonium cation of formula wherein R is an unbranched and unsubstituted C 1 -C 18 -alkyl, CH 3 O-(CH 2 CH 2 O) p -CH 2 CH 2 - or CH 3 CH 2 O-(CH 2 CH 2 O) p -CH 2 CH 2 - with p = 0 to 3; R 1, R 2 and R 3 are each independently: a hydrogen atom, unsubstituted C 1 -C 18 -alkyl, 2-hydroxyethyl, 2-cyanoethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(n-butoxycarbonyl)ethyl, chlorine, CH 3 O-(CH 2 CH 2 O) p -CH s CH 2 - or CH 3 CH 2 O-(CH 2 CH 2 O) p -CH 2 CH 2 - with p = 0 to 3, or two adjacent R 1, R 2 and R 3 radicals together with the nitrogen atom in formula are a saturated unsubstituted five- to seven-membered ring; X is an anion; and n is 1, 2 or 3; wherein the ionic liquid IL2 comprises, as cation, at least one cation selected from the group consisting of pyridinium cations, pyridazinium cations, pyrimidinium cations, pyrazinium cations, imidazolium cations, pyrazolium cations, thiazolium cations and triazolium cations, and wherein the composition comprises the at least two different ionic liquids IL1 and IL2 in a mass ratio of !L1 to IL2 in the range from 3 to 18. a) pretreating the plastic with a composition C comprising at least two different ionic liquids IL1 and IL2, the first ionic liquid IL1 comprising, as cation, at least one alkylammonium cation and the second ionic liquid IL2 comprising, as cation, at least one aromatic heterocycle having a delocalized cationic charge and comprising at least one nitrogen atom; b) treating the plastic from step a) with an activator composition A comprising at least one ionogenic and/or colloidal activator; c) treating the plastic from step b) with an accelerator composition B comprising an acid and/or a reducing agent; d) chemically depositing a metal layer, by treating the plastic from step c) with a coating composition M1 comprising at least one metal salt and at least one reducing agent; e) electrochemically coating the plastic from step d) with at least one further metal layer, by electrochemically treating the plastic from step d) with at least one coating composition M' comprising at least one metal compound, R is an unbranched and unsubstituted C 1 -C 18 -alkyl, CH 3 O-(CH 2 CH 2 O) p -CH 2 CH 2 - or CH 3 CH 2 O-(CH 2 CH 2 O) p -CH 2 CH 2 - with p = 0 to 3; R 1, R 2 and R 3 are each independently: a hydrogen atom, unsubstituted C 1 -C 18 -alkyl, 2-hydroxyethyl, 2-cyanoethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(n-butoxycarbonyl)ethyl, chlorine, CH 3 O-(CH 2 CH 2 O) p -CH s CH 2 - or CH 3 CH 2 O-(CH 2 CH 2 O) p -CH 2 CH 2 - with p = 0 to 3, or two adjacent R 1, R 2 and R 3 radicals together with the nitrogen atom in formula are a saturated unsubstituted five- to seven-membered ring; a hydrogen atom, unsubstituted C 1 -C 18 -alkyl, 2-hydroxyethyl, 2-cyanoethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(n-butoxycarbonyl)ethyl, chlorine, CH 3 O-(CH 2 CH 2 O) p -CH s CH 2 - or CH 3 CH 2 O-(CH 2 CH 2 O) p -CH 2 CH 2 - with p = 0 to 3, or two adjacent R 1, R 2 and R 3 radicals together with the nitrogen atom in formula are a saturated unsubstituted five- to seven-membered ring; X is an anion; and n is 1, 2 or 3; wherein the ionic liquid IL2 comprises, as cation, at least one cation selected from the group consisting of pyridinium cations, pyridazinium cations, pyrimidinium cations, pyrazinium cations, imidazolium cations, pyrazolium cations, thiazolium cations and triazolium cations, and wherein the composition comprises the at least two different ionic liquids IL1 and IL2 in a mass ratio of !L1 to IL2 in the range from 3 to 18.