If I am ''fit'' do I have a good Metabolism?

Metabolism is how your body/cells utilizes its food to function in the best possible way.

If your body is in good shape, and the cells are healthy, it will create a better functioning system /metabolism.

For example: A car that is old and badly treated will not utilize the gas you put into it, and will overall not run well.

The same with your body! Treat it well, feed it well, and your Metabolism will utilize its gas/food to the best of its ability. Like a machine!