I completely understand how certain elements will preferentially form ionic bonds and enter the rock phase as lithophiles. I completely understand how other elements will preferentially form metallic bonds and enter the iron core as siderophiles.

The distinction between ionic and metallic bonding is clear enough.

But what is it about sulfur? Why do certain elements “love” sulfur but not oxide or silicate anions? What characteristic of the sulfide bond makes metal-sulfides behave different from ordinary ionic compounds?

Does it have to do with sulfide being a larger, “softer” (more polarizable) anion than oxide?