Muscles are great furnaces for burnng calories. They burn calories even when you ae not exercising, i.e. when you are sitting, reading, watching TV or even sleeping. They increase your basic metabolic rate and burn calories even when they are resting. At the time of muscle exercising you are burning more calories and you are building more muscles that increase your muscle weight that would be good for burning more calories.
The article below will shows you how to do muscle exercises without as much effort as you think.