How can I pet a wild possum?

[Stacy]

There is a medium sized possum that keeps eating my cats food because its summer and they have fleas and I have a 9 week old daughter I keep them outside. but there is this possum that keeps eating their food and the past couple of nights I've caught him in the act he retreated to the back of the porch pretty slowly and is kinda hiding behind a shelf but when i talk to him to coax him out he peeks his head out and sniffs the air lol, i really want to pet him could i make this happen or what