Extraterrestrials are probable to exist, but I don't think that meeting them would be healthy for the human race.
If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn't turn out very well for the Native Americans -Stephen Hawking
I don't believe in aliens. In fact, I don't even care if there are/aren't aliens around us in the galaxy. They probably think the same as humans, but they think that we are aliens or strange people, obviously.
aliens are real. The ever expanding galaxy has millions of planets, and some of them must have life. Wether they are capable of space travel, that is another thing, but meeting an alien will be awesome. But a problem is that they might be hostile.
People have reported UFOs since a lot of time. We still don't know if they are real, illusions or any other unexplainable thing. The Space is concluded to be infinite, meaning that there could be thousands, millions! of other species in other unknown planets extremely far from Earth, in the mean time, they're called Aliens, and we might never discover them.