What do Aliens Want?

We could assume aliens are so different we will never understand them. But let's say for the sake of argument that they are more like us than we think. Let's say they are motivated by the same three goals we all have:

1 Sex

2 Power

3 Money

It's unlikely aliens want to have sex with us. And if they can fly here in powerful spaceships it's unlikely they want to dominate us (although they may take us all for slaves).

But money, now there's a key idea. Let's assume they want the same thing we want, a lot of money. No they don't want our paper, and they don't want our coins.

What they want is our gold. Few people understand how rare gold is in this universe. There is a lot of gold here on Earth, and probably a lot more in the asteroids. Gold is very rare and it's quite possible the aliens are coming here to take our gold.

The search for gold

If we are ever invaded by aliens there are 3 primary motivations which probably apply to them just as well as to humans.

3rd   Power:   They want to dominate/enslave/exterminate us

2nd  Sex:    They want to have sex with us

1st   Money:  No they don't want our money.  But they do want our gold.  Few people outside of the astrophysics community understand just how rare gold really is in this universe.  We are gold rich relative to just about every other location in the universe. 

So if aliens invade and it's not clear what they want, they probably want our gold.