Building a thermal break

[ThisIsMyUserName]

So I need to install a thermal break for my garage to help insulate the room, and I can't afford having a pro do it. The outer door stop, where most vinyl/etc. weatherproofing gets nailed in is some sort of metal that doesn't seem wise to nail into. I do have a wood door, so I could nail into that. The bottom is fine, but I have pretty big gaps on the side and top (I'm guessing .5 inch). Any ideas or advice? Help much appreciated!

 

[willymakeit]

Use pan head screws to install your doorstop or a wider stop if needed.