Shot peening is a cold working process of metal surfaces in which the substrate metal is bombarded with a variety of media (also known as a "shot"). Some of the different types of media used include: steel shot, cut wire glass bead and ceramic bead.

It has become a common misconception that abrasive blasting is the same as shot peening. Though both processes are similar, shot peening is used for work hardening the substrate surface which applies a residual compressive stress layer on the metal surface. Whereas abrasive blasting is used to remove paint, corrosion and surface coating etc.

Shot peening is a complex process: there are several different factors that contribute to the end result. The desired outcome of this process is a complete compressive residual stress layer that prevents any type of failure. Some factors that might affect the outcome of this process include hardness of metal, velocity, time, and angle of impingement, time, and velocity.