How do you plan to store this piece of metal? Hide or fit into interior and decorative elements, furniture or other elements in the house or garage?
I'm now thinking it can
be the furniture. The 100 dots can be in the side of a fridge or washing machine. It may not be sturdy enough to hammer though. Maybe an old PC will do, at least I can take the sheet metal off and place it on an anvil.
You mean the enclosure of a PC case to punch the holes in? That won't work, because the composition includes plastics in addition to metals.
Sheet metal strips are dirt cheap, especially those in smaller dimensions.
Also there are punching machines which can be programmed to punch holes in a certain pattern (google: "TRUMPF"), but these are for long slabs of sheet metal. Are you sure a hammer can make the small holes regularly sized?