What is one of the metabolic functions of bone?

The metabolic function of bone that is correctly identified is fat storage. Bones, particularly in the yellow bone marrow, serve as a reservoir for lipids, which can be utilized as an energy source when needed. This storage function provides a necessary energy reserve and plays a role in overall metabolic processes.

While it's important to understand the other options, they don't represent metabolic functions of bone. For example, the protection of the brain is indeed a function of the skull, but it doesn’t fall under the metabolic categories of functions associated with bone. Similarly, synthesis of blood cells is primarily conducted in red bone marrow, and while it is a crucial function related to bone, it is not classified as a metabolic function of bone itself. Finally, production of bone marrow is more about the structural support and overall function of the skeletal system rather than a direct metabolic activity. Thus, fat storage is the correct metabolic function of bone in this context.