They want to eat us, they want to experiment on us, they need our resources. No, they don't, say experts. If aliens were coming here, they would've traveled astonishing distances, which would be exorbitantly expensive. They probably have all the resources they need much closer than here. And, even if they did have a good reason to come here, they probably would send robots, anyway.
A more likely scenario would be radio contact with an alien civilization. If we receive signals from alien lifeforms, "We can assume that any civilization that we receive a signal from is more advanced than we are," says a NASA scientist. So now you can rest easy, and stop worrying about becoming the pet of aliens. They're not coming.