Hi! Don't know what level of detail you need but I can try and help (nearly a final year medical student).
Liver has a role in metabolism you are right - it metabolites fat, carbs and protein. More specifically it synthesises cholesterol and other fats, glycogenesis (making new glycogen)/gluconeogenesis (making new glucose), and synthesises proteins, respectively.
Other roles of the liver include making chemicals for clotting (to help make blood clots), metabolism of drugs and alcohol, bile production.
In terms of RATE of metabolism (I.e. how quick your body does stuff) your thyroid gland in your neck is responsible. The more chemicals your thyroid produces the quicker your body's metabolism is and vice versa.
Tried to keep it as simple as possible! Feel free to ask questions