That's quite a big hole to drill. If I were doing this I would use a hole saw and a 1/2 inch drill. Here is a link to the bit I would use. 1PC 20mm High Quality Metal Hole Saw Cutter Drill Bit Heavy Duty
Do not use a cheaper bit, because it will not be up to the task.
Once you have the center of the hole marked, use a center punch and hammer to create a dimple in the metal. The dimple will keep the pilot bit from moving when you try to drill the hole. Here is a link to a center punch that will be adequate. Craftsman 1/2X6" CENTER PUNCH
When you are drilling the hole, it is best to have the drill turning slow and drip cutting oil on the bit. If you try to drill too fast or do not use cutting oil, it could heat it up and dull the teeth on the saw. Here is a link to the cutting oil I use. shopyourway.com/oatey-32-oz-dark-thread-cutting-oil/161121447
Be sure to use safety glasses and keep a firm grip on the electric drill. The hardest thing is making sure the bit does not catch and twist the drill in your hands. Mark