Dumbbells can be used alone or with a bench. Whatever muscle group you wish to target, there are numerous exercise options to reach your goals. You can perform hundreds of exercises with dumbbells alone. With the addition of a bench, this number increases further as you can perform exercises such as dumbbell bench presses and lying flys, which target your chest, triceps and shoulders. A bench can also come in useful as an additional, optional support for other dumbbell exercises.