You could, but metal doesn't rust like that, the surrounding metal (within a quarter inch or so at least) is VERY thin.
If you see just small holes, it is rusting from the inside out and the back side is SHOT. Poke the hole with an awl or screw driver and you will see what I mean.
To answer the question, yes you can SOMETIMES weld up small rust holes just like that. The problem is it is rarely that simple and the metal is rusted too thin surrounding the hole.