No more than asphalt. With proper underlayment, the same layers that attenuate sound on asphalt do the same for metal — most homeowners report it's quieter than expected.
No — and if struck, metal disperses energy safely rather than burning the way wood or asphalt would. Virtually every commercial high-rise uses metal roofing.
Sometimes — we inspect the deck first and give you an honest answer. If the decking is sound and in one layer, it's possible. If not, we'll tell you why.