When you want to cut sheet metal you need to use tin snips. There are different types of tin snips, but the offset compound tin snips should let you cut sheet metal in all different ways.
Step 1 - Straight Cuts
To start, draw the line you want to cut into the sheet metal with a marker pen. Pencil won’t work. Put on gloves and safety glasses before you pick up the tin snips to cut sheet metal. Open the jaws of the tin snips as wide as possible and bring down along the line, closing the tin snips all the way. As you make your cut, roll away one side of the sheet metal to give yourself easier access to make the cut.
Step 2 - Cutting Holes
Mark the hole you want to cut on the metal with marker pen. Next take a flathead screwdriver and hammer and punch a hole into the middle of the hole area. It needs to be big enough to take the tip of the tin snips as this is the starting slot for the hole. Cut to the edge of the marked hole and then around. With some tin snips you’ll work in a clockwise direction (green handled) and other counter clockwise (red handled) to complete the cutting of the hole.