The low density metallic materials aluminum, magnesium, and titanium are important in many segments of the world economy, ranging from aerospace to sports equipment. The importance of cost is strongly dependent on the industry being considered: in the construction and automobile industries, cost is extremely important, while in the aerospace and medical industries, performance is emphasized over cost. This paper provides an overview of the synthesis, processing, microstructures, mechanical properties, and applications of these lightweight materials and discusses the importance of cost-effective processing.