I'm with Robot on the Dewalt piloted drill bits.
Absolutely great with sheet metal.

I bought a set of these when I already had the shop packed up for moving.
They were terrific on drilling the sheet metal legs of my 16' long workbench so I could bolt some long angle steel to the legs for reinforcing and skidding.
Had to load the darned thing by myself - wasn't too bad using the boat trailer winch on a stand inside my enclosed car trailer to drag it on board.

The bits look like they would be tough to sharpen so they're dedicated to sheet metal use only nowadays.