Provided are a metal line, a method of forming the same, and a display using the same. To increase resistance of a metal line having a multilayered structure of CuO/Cu and prevent blister formation, a plasma treatment is performed using a nitrogen-containing gas and a silicon-containing gas or using a hydrogen or argon as and the silicon-containing gas. Accordingly, a plasma treatment layer such as a SiNx or Si layer is thinly formed on the copper layer, thereby preventing an increase in resistance of the copper layer and also preventing blister formation caused by the damage of a copper oxide layer. Consequently, it is possible to improve the reliability of a copper line and thus enhance the reliability of a device.