NOVELTY - The metal composition (2) comprises one or more reactive metals in major proportion, and at least one alloying element in minor proportion.    USE - Metal composition is used for manufacturing apparatus e.g. oilfield (oil and gas reservoirs) element such as valve operating balls, valve operating darts, plugs, proppants and well-bore fluid diversion devices used for fuel cell, medical device, automotive device, aerospace and power plants (all claimed) and for actuators, sensors, switches and sealing of lower layers during fracturing operation.    ADVANTAGE - The metal composition is controllably reactive, degradable under defined conditions and has high-strength.    DETAILED DESCRIPTION - The metal composition comprises one or more reactive metals in major proportion, and at least one alloying element in minor proportion. The metal composition has morphology selected from partially or entirely crystalline or amorphous structure, powder metallurgy like structure comprising reactive composition, or composite and hybrid structures comprising one or more reactive metals and alloying element. The reactive metal is selected from aluminum and elements of column-1 and column-2 of periodic table such as calcium and magnesium. The alloying element is selected from lithium, gallium, indium, zinc, bismuth, tin, copper, silver, cadmium, lead, calcium, magnesium and/or aluminum. The metal composition is selected from calcium-magnesium alloy, calcium-aluminum alloy, calcium-zinc alloy, magnesium-lithium alloy, aluminum-gallium alloy, aluminum-indium alloy or aluminum-gallium-indium alloy. The metal composition is further selected from metallic alloys, metal-matrix composites, composites of degradable metals and polymers, ceramics, metallic-based nanocompositions, coated metallic compositions, multilayered and functionally graded compositions that degrade on exposure to fluid. The fluid is selected from aqueous fluids, water-based fluids, organic fluids, liquid metals, organometallic liquids comprising compound of formula RM, where R is carbon, silicon or phosphorus and M is a metal. The metal composition is coated on a substrate selected from metal, plastic or ceramic. The oilfield element apparatus comprises a relatively inert component selected from polymeric composition, metals that melt in well bore environment, acid soluble compositions and frangible ceramic compositions. The polymeric composition comprises natural polymers, synthetic polymers, blends of natural and synthetic polymers, and layered versions of polymers.    DESCRIPTION OF DRAWING(S) - The drawing shows the cross-sectional view of the apparatus formed using the metal composition.    Metal composition (2)    Subcomponent (4)    Corrosive fluid (6)    Pipe (8)    Flow direction of subcomponent towards metal composition (P)