Dude, before you kill yourself, you need to know what kind of metal you're going to cut. Circular saws are made mostly for wood, but if you get a blade for non ferrous metals, you cut cut aluminum with it, and I wouldn't cut anything thicker than 1/8"

If you're trying to cut some light steel, you need a chop saw with cut off wheel type of blade, or you could do it with a grinder.

If you're trying to cut heavier steel tubes, or stainless, you need either a sawzall or a bandsaw. You could also cut them with a grinder, but you will burn the finish badly.

They also have something called plazma cutters, but its probably out of your price range.

In any case, no matter what you cut, dont do it with a wrong blade.