What are some commonly known facts that are too bizarre for you to believe to be true?
For me it is the fact that our blood contains iron. I earlier used to believe the word stood for some 'organic element' since I couldn't accept we had metal flowing through our supposed carbon-based bodies, till I realized that is where the taste and smell of blood comes from.
Hate to burst your bubble, but the calcium inside your bones is not in a metallic form but as calciumphosphate. So no metal frame but one made of a salt I guess.
The thing that started this conversation is hemoglobin, which is also not metallic but a protein. I don't think anyone was confused and thought that there's actually shiney silvery elemental metallic calcium in our body.
The OP literally said: "Metal flowing through our supposed carbon-based bodies." So I don't think it's unreasonable to assume that there could be some confusion.
Your bones are not dead rocks! They are living organs that happen to have a lot of sturdy calcium structures in them. They do a lot of other stuff besides hold your body up. They store minerals for all the other stuff your body needs minerals for; that's why osteoporosis is even a possible failure mode. Your bone marrow produces white blood cells for your immune system, too.