I used an angle grinder, jig saw/sawzall, a skil saw with a 7 inch carbide blade for cutting aluminium, die grinder, shear, bandsaw if the clearance was good, aviation snips, and router with a carbide bit for aluminum.
I have used a chisel to score a line in 1/8 to 3/16 steel, then put it into a vice and used vice grips to bend it into breaking along the line, or a small sledge hammer to bend it over so it would break.
Same goes with router, score a line and bend the metal until it breaks or use a angle grinder. I have used milling bits in my drill press for use on aluminum or very thin gauge steel, keep in mind the tool is not designed for that particular use, but can be used if common sense prevails.
Metal chop saw, basically what ever you can think of that might do the trick , do it.
Al