A lot of air moves under the metal but as stated I would also put laths down then put ridgid foam between that. Air can move through the ridges, although I have never heard of an ice dam in the south so air movement is not that big a deal here.
If you go metal, stack the sheets then measure where your slats are or where you want you screws or nails, then drill them. Yes the screws are slef drilling but you want to have every screw line up in all directions and this will make your life easier to boot. Use mastic between sheets and stitch screws. On the ridge you can use a flat rolled flashing but get the vent stuff to put under so the birds stay out. The ends, lat down a 2x2 drip L, it has a sort of turn out so water does not go around, then run the metal about 1" beyound that. The sides, they make a thing for that as well, you can skip the special ridge part just trim the end caps to overlap and use stitch screws.
If you have questions e-mail me and I will try and get some pics of mine. I might have to go on a job soon so if I don't get back with you right away I am not ignoring you.