Then it would depend on their intentions. Best case scenario, they'd want to prevent nuclear destruction in Ukraine. Worst scenario could be almost anything.
There's also the possibility that cv5 probably alluded to, that they would be something much more spiritually sinister but pretending to be aliens from other planets. It's hard to estimate a probability to something like that, but IF we assume that the phenomenon of UFOs and the phenomenon of abduction experiences are directly related, then this idea has some plausibility from the apparent fact that such abduction experiences are often accompanied by an anti-Christian message by these "beings".