Imagine trying to explain the concept of dancing to aliens. “Well, you see, Mr. Alien, when we hear melodic sounds we humans start…er… moving, swaying, and twitching our feet and bodies in random, spontaneous motions…” amirite?

The aliens would be like "You call THAT a moonwalk?"

not to mention, certain people act like they're are ass fucking one another in a large group.

It would probably be even weirder due to the fact that you are explaining something to an alien...

I would say "rhythmic" instead of "melodic."

Aliens invented dancing.

Kissing would be weird to them to, as kissing is weird/unknown to many cultures on Earth.