Regardless of how much you already know about metabolism, here are a few important points to remember. First, it's a very complex process that deals with how your body produces energy from protein, fat, and carbohydrates/sugars and how it stores that energy. Second, when people talk about their metabolism, they're really referring to their metabolic rate: how much energy/calories your body burns in a day. Metabolic rate is not to be confused with your resting metabolic rate, which is how many calories your body needs at rest for basic functions like breathing.