Caulking/Sealing Around Shop Windows? Best way? Advice

[MTDIYer]

I had a garage/shop built. I am working on finishing it off myself. The inside is thin sheet metal and there a gaps of various sizes around the 3 windows. The shop has a lot of flies in it, and I was wondering about sealing/caulking the gap around the windows, wondering if that might help the fly problem, or simply make it look a little better or insulate. It is hard to take pictures of the windows because of the light coming in. But I am including a few. I am looking for advice on what to do, what materials to use and how to do it. Thanks







I can add more detail or explain more in reference to these pictures if that would be helpful. Thanks.