Masonry bits have a carbide tip, which allows you to cut harder metals. However, they have no cutting geometry, so they do not work well on materials that have tensile strength. The flat edge/no geometry allows them to hold up better in materials like concrete that basically only have compressive strength. In metals, you need something that actually cuts. Any decent grade "High Speed Steel" (HSS) bit should work fine, or a titanium nitride coated bit or cobalt bit will work even better (or carbide drill intended for metal, but now you're talking $$$). Spring steel is harder than standard mild steel (like plate or tubing), but still can be drilled with a decent quality standard drill bit.
