I want to plant something in a large pot, perhaps supported by a metal trellis

Whatever you put in there, if you put a hummingbird feeder in it, keep it away from your house. The sugar water may drip and the ants will come marching in. I moved mine when that happened but the ants didn't march away with it. They still visit my home. I have rose of sharon bushes and the hummingbirds always come while they are in bloom. I don't know how they will do in a pot, though.