It's pretty much a given that Solagleo and Lunala as they have been shown so far do not represent the Sun and the Moon themselves. They are both weak to types associated with the Sun and Moon, while Solagleo is thought to be the alchemical Lion Vitriol that devours the Sun.

So whether the duo change types at some point, or there are two more legendaries that actually represent the celestial bodies, or there is one legendary that represents both, what do you think the typings will be?

No doubt the Sun half will be part Fire type, but what about the Moon half? So many types are used to represent the moon in the games so far: Cressila and Darkrai, the Lunar duo are Psychic and Dark, Lunatone is Psychic and Rock, learns a few Fairy moves, and yet was updated recently to be able to learn a few Ice TMs (directly opposing Solrock who is strictly Fire). Then we have Clefairy, the Moon Pokemon, which is pure Fairy.

The Sun half is a little easier, with only having Fire type moves on Solrock, Volcarona being the Sun Pokemon (along with Sunflora). Although interestingly enough, the Jirachi's Doom Desire is Steel type, just like Solagleo.

So all in all we have

Moon: Psychic, Dark, Fairy, Ghost, and Ice
Sun: Psychic, Steel, and Fire