is metal halide for future searches.
Is this in a fixture? if so give us the model number.
If not, find the ballast that it's wired to and see what wattage it is. MH
comes in several different wattages and it needs to match to your ballast.
Also, there's 2 forms of MH
lighting, was it the big bulb or a small bulb?
Moving this to the general hardware forum.