Several factors come into play in order to answer this question fairly. Yes, denting is possible, but in most cases, preventable. First, consider the gauge of the metal roofing you’re planning to use. A thin, economy panel will of course be more prone to damage than a stronger, premium panel. If you live in a high-hail zone, make sure you select a heavier gauge panel, 26 ga or more. Second, the panel profile you select will have a great affect on the overall strength of the panel to resist deformation. A panel with many ribs and veriegation will be inherently stronger than a flat panel. Third, panels are far more durable if they are installed flat against a solid deck. And finally, don’t forget about the trim. Trim is the most prone to damage during a storm (gutters, rakes, ridgecap) so make sure to use a heavier gauge metal for these as well. If dents do occur and they’re only slight, a good hot summer may cause them to lessen or nearly disappear. Unlike composite or shake roofs, hail damage on a metal roof is merely cosmetic, and does not affect the water-tight integrity of the roof.