A pre-treatment method of plating and a plating system can perform a uniform plating process in which sufficient adhesivity on a surface of a substrate is obtained. The pre-treatment method of plating includes a coupling layer forming process of forming a titanium-based coupling layer 21b on the surface of the substrate with a titanium coupling agent; and a coupling layer modification process of modifying a surface of the titanium-based coupling layer 21b with a modifying liquid after the coupling layer forming process.

A metal material comprising: a base material; an oxide layer disposed on a surface of the base material; and a metal layer disposed on a surface of the oxide layer, wherein the base material includes aluminum, the oxide layer includes aluminum, nickel, and oxygen, the metal layer includes nickel, and an average thickness of the oxide layer is no less than 50 nm and no more than 250 nm.