For most homes, attic ventilation is critical. It helps avoid unhealthy high moisture levels which can result in condensation and even mold. It also helps reduce home heat gain and air conditioning costs in warm weather. And it plays a huge role in avoiding winter rooftop ice dams in northern climates. So, yes, your metal roof can, and usually should, be vented.
With the metal roofs we manufacture, venting can be done with our matching Perma-Vent or Hi-Flow Vent systems. Many commercially available roof and ridge vents can be incorporated into our roof systems as well. If your home has a conditioned attic space where the roof deck is insulated, you may not need attic ventilation, and a metal roof can be installed just fine over an insulated deck such as that.
Please contact us if you have any questions at all about ventilation or how to make your home more efficient and healthy. When a home is re-roofed, we suggest that all vents be replaced rather than reused.