There are many reasons that you might need to bend a cone from sheet metal. Metal cones are good for finishing chimneys, topping off certain types of outdoor fire and grill buildings and occasionally for decor purposes. Bending sheet metal is easier than you might first expect, so do not be intimidated by the process but jump right in--carefully of course.
Draw a circle on the sheet metal with a pencil compass. The pencil will make the circle, and the slight indentation where the compass has been anchored should be noted.
Cut this circle out with your sheet metal shears. Wear gloves for this, since the edges of the metal can be very sharp.
Slice the circle to the middle. Using the anchor point of your compass as a target and stopping point, cut up to it in a straight line from any side. You will now have a circle of sheet metal with a cut from one side to the centre.
Overlap one cut side onto the other. Beginning at the cut, push the pieces of sheet over each other. As you do this, you will see the circle begin to contract into a cone. Depending on how deep you want the cone, stop where needed.
Duct tape each side of the overlap. This will keep the metal from springing apart, and help protect you from rough edges. Now, your sheet metal cone is complete.
Wear gloves whenever you are handling sheet metal to avoid injuring your hands.