This chapter discusses methods of producing atomic defects in metals. Atomic defects in metals form endothermally. The required energy can be supplied thermally at elevated temperatures, or athermally. The latter is possible by plastic deformation or by irradiation. Due to their lower formation enthalpy, the concentration of thermally formed vacancies in metals exceeds the interstitial concentration. For the same reason, more vacancies than interstitials are formed during plastic deformation. On the other hand, irradiation in the bulk of a metal produces vacancies and interstitials in equal numbers (Frenkel pairs). Thus vacancies can be produced by heating a metal (to not too high temperatures, to prevent the formation of vacancy pairs and interstitials), while the production of solely interstitials in the bulk of a metal is impossible. The stability of atomic defects at a given temperature depends on their mobility, and on the presence of sinks. If point defects are produced at temperatures where they are mobile, they may form clusters or disappear at sinks (dislocations, grain boundaries, surfaces etc.). In the case of Frenkel pairs, annihilation by the recombination of interstitials and vacancies will occur. In general, interstitials in metals are mobile already far below room temperature so that they can be studied only in low-temperature experiments. On the other hand, vacancies in many metals become mobile only above room temperature. Therefore they can be retained by quenching from elevated temperatures to room temperature.