The basics
Metal roofing splits into two families: panels where you can see the fasteners, and panels where you cannot. Everything else follows from that.
Exposed fastener is screwed through the panel face. Fast, economical, and the right answer on barns, shops and pole buildings.
Standing seam and concealed fastener systems hide the fasteners under the seam, so nothing penetrates the weather surface. This is what goes on houses.
From there it is profile, gauge, and finish. Ask us and we will tell you which one your building wants.