There are many misconceptions about metabolism and how it affects weigh loss or gain. Simply put, your metabolism rate determines how fast or slow calories are used up by your body. If your body uses up calories slowly then those extra calories not used right away are going to be stored by your body as fat for later use. If your body uses up your calories fast then your body will either maintain its weigh or lose weight.
How does your body rate it's metabolism? You metabolism rate is determined by your ratio of muscle mass to body fat. Muscle uses more calories than fat does so the more muscle mass you have the faster your metabolism rate is going to be.
To increase your metabolism rate simply increase your muscle mass. That means you have to exercise with the idea of building muscle not just burning off calories. Aerobic exercise will not raise your metabolism rate but will help your heart and lungs. You will need to add weight training to your work outs in order to raise your metabolism rate.