Metal-nanoparticle composites, such as metal-boron nitride nanoparticle composites, and methods of manufacturing the same are provided. Ultrasonic casting techniques can be used to achieve uniform dispersion of nanoparticles, such as boron nitride nanotubes (BNNTs) in a metal matrix, such as aluminum. The BNNTs can be incorporated into the melt of the metal, and ultrasonic treatment can then be applied.