Cutting holes in sheet metal can be done with many different kinds of tools. The tool that you may need will depend in part on the weight of the corrugated steel. Some kinds are fairly lightweight and easy to cut, while some are heavier and therefore much more difficult to cut. When cut with power tools, it has a tendency to vibrate, causing precision cutting to be a challenge -- especially if the sheet metal is not properly supported.
Create a paper pattern of the size and shape of hole you wish to cut. Measure from the edges of the sheet metal to the point at which you wish to place the hole. Position the pattern on the sheet metal where the hole needs to go, and draw a line around it using a permanent marker.
Punch a hole through the metal using a cold chisel and mallet or drill through with a heavy-duty drill with a bit that is rated for metal. Make the incision large enough to admit the Sawzall blade. If you do not have a Sawzall or other saw that will safely cut metal, use a pair of heavy-duty tin snips.
Anchor the sheet metal firmly so that it will not move. If it moves, it could injure you or bystanders, and spoil the precision of your cut. If you are working on a roof or side of a building, you might fasten the item in place; if working on a smaller item, secure it to a sturdy work bench using clamps. Insert the blade of the Sawzall into the opening and cut along the line. If using tin snips, insert one blade of the snips in the opening and cut along the line.