I have a tin roof and am having a very hard time keeping my eves troughs in good shape and in one case on. I know the ice is the culprit but it have not found an easy way to keep it from doing the damage. Unfortunately the builder of the home put in valleys in the roof where the living room is joined to the main house. This has created a very nice place for the snow and ice to settle in. Once it is in there it doesn't move very much and not quickly at all, several of my friends have called it the "Lance Glacier". What I would like is a way to reduce or eliminate the ice and to replace the evestrough with new ones that may be a little more robust.
You could consider installing “Snow Jacks” in the valley area (clear plastic stops that screw to a metal roof). They hold ice and snow until it melts into smaller components and allows water to run off without damaging the gutters. For more information on this product call 1-800-663-6322. Or, you might call the Leafguard Gutter Company at 1-800-Gutters. Leafguard makes a very robust gutter system and they are generally sold as an installed product but they might be willing to ship them to you.