A metal halide lamp is an electric lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides (compounds of metals with bromine or iodine).

It is a type of high intensity gas discharge lamp. This lamp was developed in the 1960s and is similar to mercury vapor lamps, but contains additional metal halide compounds in the quartz arc tube that improve the efficiency and color rendering of the light.

The most common metal halide compound used is sodium iodide. When the arc tube reaches its operating temperature, the sodium separates from the iodine, adding orange and red colors from the sodium D line to the lamp spectrum to ionize the metal. As a result, metal halide lamps have a high luminous efficiency of about 75 to 100 lumens/watt, which is about twice that of mercury vapor lamps and 3 to 5 times that of incandescent lamps, and they produce a white color.

The life of the lamp is 6000 to 15000 hours. As one of the most efficient sources of high CRI white light, metal halides were the fastest growing segment of the lighting industry until 2005. They are used for large-area lighting in commercial, industrial, and public areas such as parking lots, sports fields, factories, and retail stores, as well as residential security lighting and vehicle headlights.