Measure the length and width of the tabletop. Draw the dimensions of the tabletop onto the piece of sheet metal with a marker.
Put on a pair of sturdy work gloves. Cut out the outline of the tabletop on the sheet metal using a pair of large tin snips designed for cutting straight lines.
Clean the surface of your tabletop, and place the piece of sheet metal on top. Line it up so the edges of the metal are even with the edges of the tabletop.
Screw the sheet metal piece to your table top using Phillips flat-head self-drilling screws. Install one in each corner to hold it securely into place. Add one every 6 inches around the perimeter of the table to complete the process.