Lightweight Al matrix nanocomposite received numerous attention due to their high specific strength, high electrical conductivity and high thermal conductivity. This talk will highlight two distinctive Al matrix nanocomposites reinforced by calcium metal and carbon nanotubes, respectively. For Al matrix calcium composite, a complete processing-structure-property relation will be discussed with the aid of analytic modeling to help design the optimal microstructure for strength and electrical conductivity. For the Al matrix carbon nanotube composite, the focus would be on resolving the processing challenge of carbon nanotubes reinforced metal matrix composite, such as the dispersion, the oxidative and reactive damage control. The successful processing of Al carbon nanotube composite can be measured by the amount of electrical conductivity or thermal conductivity increase over that for pure Al.