Do you think it really adds more than its cost to the resale? Is that $5000 more if you sold it today, or in 20 years?
I'm pondering this now, because I've been semi in the market for a new roof for 6+ years - our comp roof is positively aged (not in a "aged like fine wine" way, either) and I've figured metal was likely the best roof - but I also don't want to increase the already ridiculously high insurance cost, and given that I'm hoping we won't be here long, the more immediate resale value question is pretty important.
I suspect that the cost of a metal roof is significantly higher than for a good comp one. Not 10%, probably closer to 50%. Very few roofers in my area do them, either, so that probably drives part of the price differential.
My guess is that a good metal roof will outlast a comp roof, but that doesn't matter much in the near-term resale value. Saying a metal roof has better fire characteristics than a comp roof does, of course, but I'm not sure how much of a boost in the emotional "it's so much safer" to a buyer will be offset by higher insurance costs, since they don't seem to care that much about what the roof is, as long as it's recent.
It would be interesting to find a scientific study about the monetary advantages, but I doubt that's been done at all let alone recently when insurance costs have gone through the roof.