Metal/metal oxides and conductive polymers are common supercapacitor electrode materials, revealing high power density as well as long cycle life. In composites, graphene and metal oxides displayed the combination of the excellent cycle stability of graphene and the high-capacity properties of metal oxides which remarkably improve the comprehensive properties of nanocomposites. The current developments of metal/metal oxide decorated graphene (MGr) composites in the field of electrochemical capacitors are elucidated here on account of their synergistic properties. It is demonstrated that, in comparison with their individual influences, MGr composites have attained substantial improvement in rate capability, capacity, and cycling stability. Mainly, an overview of the characteristics, preparation approaches, and application of graphene (Gr) is outlined. Mechanism of different types of electrochemical capacitance is described explicitly. Finally, the future prospects and challenges of MGr composites have been discussed for energy storage.