Nano-structured metals and their alloys possess superior mechanical properties.The defects inside or on the surfaces of the nano-structured metals, including grainboundaries, dislocations, twin boundaries, voids, cracks, the second phases, etc., can influencethe materials strength and toughness significantly through their nucleation, evolutionand interactions. This review article surveys the advances in microstructure characterizationand mechanical testing, as well as computations and simulations on strengthening andtoughening mechanisms of several novel nano-structured metals. It is also proposed that thecomprehensive investigation is necessary on nano-structured metals to obtain the specificmechanical behaviors and primary deformation mechanisms at atomic scales.