My Kepler Bb people live in a part of their planet saturated with iron. But not in the metal form. Rather in an oxidized form called an ore. Every time they dig a chamber, each person finds at least 1 iron ore. But in order to get further in their technology, they need to use the iron ore somehow. Iron ore by itself is fragile and 100% iron is too soft for most tasks.
Ironically, to make iron from iron ore, they need iron in the metal form.
This is a problem, They need iron to advance technology but they need iron in the metal form to make more iron. So how are they going to get iron if they don't have iron(not in a metal anyway)?