So, when is cost not important in anything? It doesn't matter what commodity we may be talking about, cost always matters. So of course cost is important when you are thinking of installing a metal roof. There are some important things to consider and some questions you should ask before making your decision. One question to ask is, Why am I paying more for a metal roofing product than I am for an asphalt roofing product? And, why should I choose a metal roof over an asphalt roof? Well, there are several reasons.