As I mentioned in another post why would the aliens want to fight us? Would it not just be easier for them to spray a chemical in the atmosphere that kills humans? We currently have that technology and I'm sure the aliens would also.
They'll be so advanced, it'll be like one of us coming across a can of earthworms and deciding we wanted something the earthworms had. Don't ask me what a can of earthworms could possibly have that we would want, or what we would have that super advanced aliens would want. IF we wanted it, we'd just dump the can out and take it, all their squirming around notwithstanding. Oh, the worms might describe it as fighting, but to us it'd just look like a bunch of futile squirming around. It would be so ineffective, we wouldn't even recognize it as fighting.
I suspect that is where we would be vis-a-vis any aliens who came to Earth.
Incidentally, did you know that the average star out there is one to two billion years older than our Sun? We can expect that any advanced civilization we encounter will be, on average, roughly, one to two billion years more advanced than us, all other things being equal.
No, boys and girls, it IS NOT a Star Trek universe out there. We WILL NOT be boldly going where no man has gone before, looking for new life forms to make friends with. Instead, if we know what's good for us, we will be creeping around in the shadows, hoping not to be noticed, like tiny little rodents scurrying around at the feet of enormous herds of Tyrannosaurus Rex.