A progressing cavity pump/motor includes a stator (12) having a metal interior surface (14) and one or more spiraling internal lobes (16). The rotor (18) has a metal exterior surface (20) and one or more spiraling external lobes (22) for cooperating with the stator to form progressing cavities between the stator and the rotor during rotation of the rotor. At least one of the stator interior surface and the rotor exterior surface include a plurality of spaced grooves (30) in the respective surface, such that fluid flowing to a gap between the stator and the rotor is disrupted by the spaced grooves to reduce fluid leakage between the stator and the rotor.