Building a Metal Farm in Subnautica 2 is absurdly useful when it comes to duplicating rare metals like Troilite. Later on, when you're repairing the Alien Power Plant, you'll need a lot of this material and there isn't very much to find on the map, so using a Metal Farm is a much better approach.
You'll need to have reached the Alien Ruins area via the Tadpole Pens to do this, and you'll also need the Tadpole Depth module. Otherwise, here's what you need to do to unlock the Metal Farm blueprint and how it works.
