couple issues with metal roofs, snow and gutters.. depends on the location (weather) pitch of the roof and building access (Doors)...
I have had winters when the snow in October didn't leave till April just build up and kept coming.. had warm ups in mid winter some times where it would melt but not slide off (I have a 4/12 roof) that's a problem as the gutters fill up then freeze connected to snow and the whole works comes off when it does let loose.. if you want gutters and no stops put the gutters lower than normal so snow shoots off roof without hitting the gutter edge.
if your not daily occupants
if you have snow come off and your not there to deal with it, it will be like concrete frozen and you won't be able to get a storm door open.. as to Morton not wanting snow guards its probably they are marginal on the snow load specs for the building.. I went with a builder that knows snow country and builds for 200" snowfall seasons.. long story short put them where you need them walk ways, doors but otherwise let it come off.. as far as falling snow/ice from one height to another
View attachment 477739View attachment 477740here is a couple work pictures from this spring..