Standing-seam and exposed-fastener metal, in any colour you want. It costs more than shingle up front and it is the last roof a lot of people ever buy.
A shingle roof around here is a 20 to 30 year decision. Metal is a different bracket entirely, with paint warranties running 30 to 50 years. If you plan to be in the house a long time, you are often buying one metal roof instead of two shingle roofs, and that is where the numbers turn.
It also sheds weather better. Rain and hail come off metal rather than working into it, and there is nothing for wind to get under the way it gets under a lifted shingle tab. On the ridges and exposed lots around Chattanooga that matters more than it does down in a sheltered neighbourhood.

Residential metal, done by the same owner-run crew that does the shingle work.
Same crew, same standard, on both sides of the state line.
Owner-run since 1994, BBB A+ and 4.9 from 40 Google reviews. Free written quotes across Greater Chattanooga and North Georgia.