That's a very good idea. But there needs to be more than just metal to make a car. You need electricity, fuel, and oil. The fuel, oil, and electricity can be in the mines where you can convert the fossil fules into fuel, oil, and electricity. You should also make a thirst mod. You can collect underground water, or ocean water that can become freshwater for you to drink. It acts just like the hunger mod, but with different needs.