so many
Assuming you have sun, the options are wide open. You'll need floating plants, draping pants, submerged plants, and tall plants.
You'll want a very small water lily, even one can cover your surface, so don't get two. Lotus if small can substitute, it will carry its leaves above the surface eventually.
Parrots feather is a nice draping plant, water clover too, and both can come into the aquarium. These give your fish a place to hide from predators, racoons, snakes, herons, the neighbors' bratty kid.
Submerged will also be familiar to the aquarium keeper, with anachris, foxtail, hornwort, and valisnaria. These are to add oxygen to the water, but remember they draw oxygen in the night so don't let them take over.
Tall plants... iris, sedge, papyrus, cattail, lots more. If you have tall plants anywhere around the pond, you wont need them in the pond, there is a limit to how much stuff you can cram in without losing site of the fish.
It matters what fish you are keeping, koi will destroy most plants, and large goldfish will dig too but not qiute as bad.
Lot's of good plant sources have photos on line. Better to pick up in person locally if you can, though.
And, it will cost $$ to get it 'trimmed' back.