Light metal and alloys possess high strength-to-weight ratios and low density, and are generally defined by low toxicity as opposed to heavy metals, except for beryllium. Lighter vehicles that are designed for consumers, as well as the industry and military sectors, consume less fuel and provide a better performance. In addition to carrying larger loads, lighter vehicles can travel the same distances at reduced cost and release less carbon dioxide. Metal matrix nanocomposites (MMNCs) with a light metal matrix are hybrid materials that have recently become the focus of interest for materials scientists and industry. The lightest metal that is a pure element is lithium, which has a density of 0.534 g/cm3. The most important light metals are aluminum, magnesium, titanium, beryllium, and lithium. Another important development of the late 19th century was the separation from their ores, on a substantial scale, of aluminum and magnesium. Light metal and alloys possess high strength-to-weight ratios and low density, and are generally defined by low toxicity as opposed to heavy metals, except for beryllium.