Aluminum is similarly abundant in the Earth's crust. Most common element after oxygen and silicon, twice as abundant as iron. Correctly tempered and hardened aluminum is lighter and much stronger than iron.
The sole reason aluminum isn't the "default metal" in the way iron is, is that it's so much harder and more expensive to smelt:
Electric power represents about 20% to 40% of the cost of
producing aluminium, depending on the location of the
smelter. Aluminium production consumes roughly 5% of
electricity generated in the U.S.[26]
I agree that pretty much everything manufactured on the Moon is going to be made of aluminum, for precisely those reasons, but needing a "little" solar power is underselling it a little.
But the two things you have on the moon - unrestricted view of the sun, aluminum dust lying around in piles - means its certainly the easiest of the alternatives. That's the point.
It's aluminum-containing dust, not bulk metallic aluminum. All of the aluminum-containing minerals on the Moon have the aluminum atoms bound to oxygen, silicon, etc. Smelting aluminum is expensive because oxygen bonds to aluminum very tightly, and requires a lot of electricity to pull it off.
The sole reason aluminum isn't the "default metal" in the way iron is, is that it's so much harder and more expensive to smelt:
I agree that pretty much everything manufactured on the Moon is going to be made of aluminum, for precisely those reasons, but needing a "little" solar power is underselling it a little.