Sheet metal can be cut with metal snips, sometimes called tin snips. The models at left are called aviation snips. They have added leverage to help you cut through thicker and tougher metal. The three on the right have serrated edges (jagged edges) that make it easy to cut through metal, but they leave a rougher edge on the part that must be filed smooth. The reason that there are three of these snips is that each has a set of jaws to cut in a specific direction: left curve, right curve or straight. I use the yellow set (straight) most often.

The red set on the far left has smooth jaws and leaves a nicer edge. It also has offset jaws that keeps your hand away from the sharp edges of the cut metal. I usually wear leather gloves when using snips to protect my hands. Sometimes I can't make the cuts while wearing gloves so I wrap my fingers with duct tape to keep me from getting cut.