Woodpeckers sometimes hammer on metal siding or flashing, resulting in an annoyingly loud noise. It’s almost always a male, and he’s not looking for insects; he’s discovered that his pecking can be heard from much farther away.
It looks like the same hammering behavior that's typical of all Woodpeckers. But it’s a signal telling females that he’s on the prowl, and for other males to stay way. If it doesn’t work (and it rarely does), he’ll eventually go try something else.