 Therefore, it's more common for a metal halide to be used when the plants are on display in the home (for example with ornamental plants) and natural color is preferred.Metal halide bulbs need to be replaced about once a year, compared to HPS lights which last twice as long.Metal halide lamps are widely used in the horticultural industry and are well-suited to supporting plants in earlier developmental stages by promoting stronger roots, better resistance against disease and more compact growth.