In a Tribology Letters paper, we employed molecular dynamics simulations to study the frictional behavior of a tip-on-substrate contact between a pure metal (Ag as an example) or a metal alloy (Ag-Cu as an example). We showed that in pure metals, sliding occurs along the crystallographic slip planes, whereas in alloys shear is accommodated by grain boundaries. In pure metals, there is significant grain growth induced by the applied shear stress and the slip planes are commensurate contacts with high friction. However, the presence of dissimilar atoms in alloys suppresses grain growth and stabilizes grain boundaries, leading to low friction via grain boundary sliding.