For engineering applications, structural materials must possess a balance of static and dynamic properties. Strength, ductility and fatigue life are often critical properties. While ultrafine grained materials (UFG) invariably possess high strength, the level of ductility and fatigue life often limit the applicability. To obtain balanced mechanical response in UFG lightweight alloys, consideration must be given to the details of the microstructure and the microstructure/mechanics intersection. Some examples of change in overall mechanical response in UFG aluminum and titanium alloys will be highlighted. The relative role of microstructure and mechanics will be discussed.