A metal halide discharge lamp comprises a lamp body and a chamber formed within the body. A pair of electrodes extends into the chamber and have electrode tips spaced apart from one another. A discharge medium composition is sealed within the chamber that generates a plasma, which generates visible light. The composition comprises a rare gas, a first metal halide that produces a luminous flux and a second metal halide that generates a desired lamp operating voltage. The composition may also comprise a metal, sealed in the chamber, in elemental form and is not derived from the first metal halide or the second metal halide. The second metal halide serves as a substitute for mercury for purposes of generating desired lamp operating voltage.