Make sure there is sufficient pitch, particularly if there will be seams. We bought a house last year with a new metal roof and had to replace with rubber because it was leaking, particularly when snow would melt and seep under it. The rain was also fairly loud on it. It was somewhat soothing when it was a steady light rain but a bit alarming in heavy torrential rain! I may have been more sensitive to it though since any precipitation meant checking for leaks
