Metal roofs don’t prevent ice dams. The root cause of ice dams is improper attic ventilation and inadequate attic insulation. If your attic space doesn’t have enough insulation and ventilation, ice dams can still form on a metal roof. Ice dams result from a problem that could exist for any attic space and roof. Heat still rises, and with lack of insulation and ventilation, the snow on the roof melts, runs down and re-freezes at the eaves — even if it is a metal roof.