The phrase "metal surfaces" refers to the outermost part of objects that are made of metal. It indicates the smooth, shiny, or rough parts of an item that are made out of metal material. Full definition
While such «steering» of the molecules is seen on metal surfaces, it occurs at much shorter distances. (pnnl.gov)
She attempts to set up an exchange between her own soft human body and the cold metal surfaces of the tunnel. (contemporaryartsociety.org)
This project is aimed at using the interaction of light and electrons in metal surfaces for the development of novel components for data transmission between chips. (sciencedaily.com)