Abstract: A capacitor and supercapacitor design are based on metal-foam electrodes. An electrolytic capacitor has a metal foam dielectric (e.g., aluminum oxide, titanium oxide, iron oxide, or others). An electric double-layer supercapacitor has an electrode with metal foam (e.g., copper, nickel, titanium, iron, steel alloy, or aluminum) filled with activated carbon, or graphene, or metal foam with activated carbon foam, or any combination of these to enhance the electrical conductivity and thus the power and capacity of the cell. A pseudocapacitor device has an electrode with metal foam (e.g., iron, cobalt, nickel, copper, titanium, aluminum, magnesium, tin, manganese, and stainless steel, and their alloy foams) coated with an oxide- or hydroxide-based material containing highly active zones. The pseudocapacitor metal-foam electrode can also be filled with activated carbon in the form of a slurry to further enhance its capacity.