Here's the thing: We don't love talking about hard and fast style "rules" around here. In the current menswear landscape—expressive and ebullient as it is—it just doesn't seem like the right move. But if there had to be one real rule, it'd be to understand whatever style situation is at hand, and dress for it according to your best instincts. That's not to say you need to obsess over whether the traditionalists of the world will bestow your look with some stamp of propriety, but there's some very real value in understanding where the guideposts are, and veering out of them only with a degree of consideration.
Why this philosophical preamble? Because we're about to delve into the world of formalwear, where rules abound and some people take them very seriously. You don't need to do that. But if you're going to be wearing a tux, you should probably skip the Jordan 11s and opt for a genuinely dressed-up shoe (unless you're Jason Sudekis). Patent pumps and lace-ups are the most formal and "proper" of choices, but you can also get away with smoking slippers and even classic calfskin oxfords.