The halogen/magnesium-exchange reaction has opened new perspectives in organic synthesis and has considerably extended the range of available functionalized aryl and heteroaryl magnesium compounds bearing functional groups such as ester, nitrile, iodide, imine, or even sensitive groups like nitro, hydroxy, and boronic esters. The present review Summarizes the applications of these functionalized heteroaryl-and arylmagnesium compounds for the synthesis of a wide variety of regiospecifically functionalized five- and six-membered heterocycles.