Not sure what kind of interference the metal building will cause, but you do have the option of using a wired backhaul from the router to a satellite placed inside the metal building, which should avoid the issue in the first place. Not sure whether that will give you good enough coverage, with the satellite covering inside the metal building, and the router covering everything else. But you could play around with different configurations (router in one brick building and satellite in the other, router in one brick building and satellite in the metal building, either using a wired or wireless backhaul) and see which works best. If it comes down to it, you could buy an additional satellite so that you have the router in one brick building, a satellite in the other brick building, and a satellite in the metal building.
