For the most part, build your training program around compound free-weight movements. Do the basics exceptionally well and you'll develop an impressive physique. There are, however, many machine exercises which augment the big lifts and help you build even more muscle.
One such example is the reverse-band Smith machine bench press:
Using bands and chains on extension exercises like the bench press helps to match the exercise's resistance profile to your strength curve throughout the lift. So, as you get stronger the resistance increases accordingly. As a result, your muscles are challenged across the entire range. This provides a more effective challenge to the target body part(s) and makes your training more efficient.
Powerlifters adopted this idea ages ago and have been using bands and chains on bench presses for years. Traditionally, when using bands, they've attached them from the ground up. This not only makes the lockout harder, but increases the workload on the lowering phase because the band is actively pulling the bar down. This technique is extremely effective, but also very demanding. Most lifters can only handle using this technique for a few weeks at a time.
Using a reverse band set-up allows you to get the benefits of accommodating resistance, but it's much less taxing on your recovery capacity. As you lower the weight it's gradually unloaded by the bands. This reduces the intensity of the eccentric (negative) phase and reduces joint forces in the bottom position – where you're weakest and the most susceptible to injury. You can train in this manner consistently without fear of injury or overtraining.
Why Use the Smith Machine?
There are two problems with the regular bench press and reverse bands. Firstly, where do you attach the bands? If you bench within a full power rack you can do barbell bench presses with reverse bands. Most lifters probably don't have that luxury at their gym though.
Secondly, if you're able to create a reverse band set-up with a barbell bench press, the bench you use is very likely not adjustable. This limits you to only using accommodating resistance on a flat bench. The use of incline presses will allow you to maximize your chest development, so you want to include them in your training at least some of the time.
This is where the Smith Machine comes in. It provides an easy way to attach bands from the top down. Thus, you can train your chest and triceps frequently with accommodating resistance at various angles.