A metal matrix composite was fabricated by adding particles of calcium hexaboride to a metal of aluminum, magnesium or titanium and their alloys. The resulting metal matrix composite is light weight has improved strength, increased elastic modulus and reduced thermal coefficient of expansion, thus making the metal matrix composite more useful in industry. A metal matrix composite is also formed by mixing particles of aluminum, magnesium, titanium or combinations thereof with particles of silicon lexaboride, calcium hexaboride, silicon tetraboride, calcium tetraboride or combinations thereof. The blended particles are processed according to powder metallurgical techniques to produce a metal matrix composite material.