A review of the potential of metal matrix composites and of currently active research is presented, also giving reasons for the recent acceleration of interest in this area. Two approaches are considered: (1) reinforcement, in which the high strength-modulus filament is incorporated for the purpose of strengthening the metal and (2) binder, in which the metal is incorporated for the purpose of binding together large volume percentages of filament. To provide a further introductory review, current problems in the areas of filament characterization, micromechanics, preparation approaches, filament-matrix interactions, and composite testing will be covered and illustrated, primarily with recent results from the authors' laboratory.