It has long been hypothesized that grain boundaries have features in common with glass-forming (GF) liquids. Emergent collective atomic motion and dynamic heterogeneity are symptomatic of diverse types of amorphous condensed materials, which have been identified in recent molecular dynamics (MD) simulations in a wide range of GF liquids. In addition, collective motion arises in systems that are not normally considered to be GF liquids. Our recent MD simulations have indicated that collective motion is prevalent in grain boundaries. It has also been observed in simulations of homogeneous melting of bulk crystalline Ni, the interfacial dynamics of bulk crystals, and dynamic relaxation of Cu-Zr metallic glasses. Apparently, collective atomic motion is important to understand the dynamic heterogeneity and dynamic response in variety systems. In this talk, we will discuss the effects of collective atomic motion on grain boundary migration, grain boundary self-diffusion, and formation of shear bands in metallic glasses.