Sliding contact systems are widely used as a method of exchanging power between static and movable devices. Improvement in the service life and reliability of the system is a significant challenge. The sliding characteristics of Ag–graphite brushes and Ag-coated rings have been thoroughly investigated; however, Au brushes and Au-coated rings have received comparatively little attention. The metal brush is mainly used for measurements of systems containing brushes and has been applied to the rotating body within DC power supplies of electrical equipment. Meanwhile, a sliding contact has been widely used to exchange electric power between a stationary unit and movable unit. It is important to increase the lifetime and reliability of devices that use sliding contacts. The present study investigated the standstill and contact voltage properties during the sliding of a metal brush and metal collector ring. The study further investigated the effect of lubricating oil on the contact state. Mainly, the contact voltage drop at different currents (0–2 A in 0.2A intervals) and loads (0–5 N in 0.5N intervals) was studied. Gold brush (pure gold, ⌀ 0.5 mm)and copper (two kinds of tough pitch copper, ⌀ 0.5 mm) brushes were used as the metal brush. The contact voltagedrop and the surface conditions of the brush and slip ring were observed for a copper slip ring.