Originally posted by pipo.p:

What would have made sense, indeed, in regard of some other fantasy settings, is to make raw metal incompatible with the use of eitr and portals. Exception could be silver or exotic metals (like the werewolf/vampire/faery vulnerability). But forbidding most metal-made items would have been too much a constraint, and then players should rejoice to be able to bring with swords and armor, instead of comparing nails with ingots, imo.

Would work if it wasn't so easy to build a smelter and if it wasn't possible to extract complete ingots from certain places like frost caves.

You can just headcanon it so that ingots are still considered "raw" or "unowned" enough that they cannot pass through portals. Need to work them into actually usable shape first, same way as teleporting anything on a person like their clothing and other possessions works (the way I see it anyway).

But the actual reason is still, of course, gameplay and exploration. Ship your metals during night and you'll find basically free serpent meat or even trophies.