There are some people that actually believe that the Sun is made of Fire!

Guess what? The Sun is NOT made of fire, it is a huge sphere of hot gas. Most of this gas is Hydrogen (about 70%) and Helium (about 28%). Carbon, Nitrogen and Oxygen make up 1.5% and the other 0.5% is made up of small amounts of many other elements such as Neon, Iron, Silicon, magnesium and sulfur.

Also, The sun is a star and Iron plays a whole role on most of them by nuclear fusion and stuff.

Do NOT believe me, but we don’t have other Pkmn-Type based on any other of these elements and since Steel is Iron that should be the reason why Solgaleo is part Steel! I guess GameFreak didn’t want to be that… cliché.