I can't say I've had a lot of run-ins with possums in the wild. When I was a youngster in Louisiana, occasionally as our family exited the car in wintery early night, a possum might be seen near the dog's bowl under the entry, or scrambling away from the shelter of the carport. They tended to be active at night, live hidden from us most of the time. We only saw possums when we surprised them, unannounced. Their sweet long faces were appealing, their hairless tails a little unnerving. We did come upon what looked like a dead possum once, only to look again a while later and find that it was gone. I never knew why a maintenance crew at the hospital in Texas where I worked carried off an adult possum in a net early one morning, to be removed and transferred to another location. That possum was hissing and struggling. Possums bare their teeth when they hiss and look scary, but the only time I've seen a possum hiss was when it was afraid, on the defensive. No one has ever mentioned to me getting bit by a possum.
Possums are marsupials, kin to the platypus, the kangaroo, the koala, and the wallaby. They're reported to be the only marsupial native to the American continents. Their alert, curious spirits are a peaceful part of the woods and swamps at night.