Do most people with metal roofs use gutters?
You can use gutters. I would say not particularly any more or less with metal roof than with shingles.
Depends on your building, situation, preference, location: Whether you get snow, ice, rain, leaves, pine needles...
Depending on your roof, attic, insulation, thawing/freezing... you may get ice dams on the roof or ice build up in the gutters and tear the off from the weight.
I, personally, don't like gutters. I do have one over the top of one door. My preference is to have a dormer split the flow and route water around.
Snow will slide off of a metal roof a LOT more abruptly than is usual with shingles on the roof. Depends on how steep the roof is.
I see a lot of Snow Breaks installed on metal roofs. Supposed to keep the snow up on the roof to melt instead of sliding off in a big whoosh and causing damage. If you have gutters installed high, the snow sliding off the roof can tear them right off.
We get enough snow here sometimes that I would rather have it off of the roof instead of building up and getting heavy.