The present invention relates to a method to electroplate or electropolish a metal on a substrate wherein an ionic liquid is selected from the group of N+R1R2R3R4 X− or N+R5R6R7R8 Y− is employed as electrolyte, and a metal salt added to the ionic liquid is employed as the metal source or a metal anode is used as the metal source, wherein any one of R1 to R8 independently represents a hydrogen, alkyl, cycloalkyl, aryl, or aralkyl group that may be substituted with a group selected from OH, Cl, Br, F, I, phenyl, NH2, CN, NO2, COOR9, CHO, COR9, or OR9, at least one of R5 to R8 is a fatty alkyl chain, and one or more of R5 to R8 can be a (poly)oxyalkylene group wherein the alkylene is a C1 to C4 alkylene and the total number of oxyalkylene units can be from 1 to 50 oxyalkylene units, and at least one of R1 to R8 is a C1 to C4 alkyl chain, R9 is an alkyl or cycloalkyl group, X− is an anion having an N-acyl sulphonylimide anion (—CO—N−—SO2—) functionality, Y− is an anion compatible with the N+R5R6R7R8 ammonium cation, such as a halogenide anion, a carboxylate anion, a sulphate (both organic and inorganic sulphate), sulphonate, carbonate, nitrate, nitrite, thiocyanate, hydroxide, or sulphonylimide anion.