Barbells are the most effective form of resistance training
If your goal is to build muscle mass, then training with barbells is a great way to do so. The only way you will put on mass is by placing a foreign amount of stress upon it. You do this by implimenting resistance training in your workout routine either by the use of machine resistance or freeweights. Out of machine resistance, and dumbbell training, training with barbells is generally seen as the way to build the most mass of the three.
There are many popular barbell exercises that do the body wonders throughout the various muscle groups. One of the most important things to note while training with barbells is to learn proper form. You can seriously injure yourself if you don't know what you're doing. When learning a new exercise it is best to be cautious and use light weight while trying to perfect the movement and form.
The advantage of training with barbells opposed to machine resistance for example, is the fact that barbells offer your body the ability to perform the movement naturally, whereas nearly all machines restrain your movement to the flow of the machine. That is why freeweights (barbells and dumbbells) help build stabilizer muscles, while machine resistance neglects those stabilizers.