Cold spray, initially a coating technique, is being touted as a ‘near-net shape’ manufacturing technology that minimizes material waste by virtue of the high rate of deposition. During the cold spray process, metallic bulk components can be produced by spraying metal powders at high velocity, generating bonding through severe plastic deformation at temperatures well below the melting point of the powders. To fully understand the cold spray processing of metal powders, we systematically compare and study the microstructure evolution in Cu, Ni, Al, Ti, tool steels prepared by cold spray. We show complex microstructure in these powder particles after cold spraying: nanocrystalline, nanotwins, annealing twins, gradient grains, deformation bands, dynamic/static recovery and recrystallization. The effects of gas temperature and powder velocity on the microstructure and mechanical properties in the cold sprayed samples are also discussed. Of particular interest are grain refinement, recrystallization and particle/particle bonding mechanisms of the powder particles.