There are several types of bench press machines and they can be very useful in doing this exercise as they provide the opportunity to stress on the muscles in a different way, owing to the principles of isokinetic contraction. It is recommended to alternate free weight lifting and machine bench press, as using mainly free weight lifting can decrease the overall growth  and development due to  decreased hypertrophy of the muscle fibers, characteristic for workouts with isotonic contractions.
The injury hazard in machine bench press is smaller.
Besides ensuring a specific effect on the muscle fiber, which leads to increased formation and giving prominence to the muscle outline, the machine provides the opportunity for safer exercising. The risk of being pressed or hit by the barbell is minimized as the machine is supplied with a safety lever for free body movement.
Vertical machine bench press
The vertical bench press machine, which has you seated, gives the opportunity to do an exercise for moving mass, unique with that the resistance and the movement are not shifted in one and the same direction in the horizontal plane. The resistance (the disc mount) moves vertically and the movement is done horizontally. The effect on the chest is different from that in ordinary bench press, where the resistance and the movement follow one and the same direction. In using vertical bench press machine the risks in pressing the weight upwards against the body gravity are done away with.

Incline machine bench press
The usefulness of this type of machine is in the fact that it is not necessary to balance with the barbell over the head, which hides injury hazards. Besides, the fixed position provides the opportunity for provoking a maximum number of muscle fibers and doing the exercise safely. The isokinetic contraction offers a variant of muscle contractions in incline press such that additional growth and development are ensured.

Decline machine bench press
The already mentioned advantages of the bench press machines become clearer in doing the exercise on a decline machine. Another advantage here is that the resistance angle is changed first inwards, then upwards and finally backwards. This exercise stimulates the activity of the two heads of the pectoralis major muscle and includes the pectoralis minor muscle into the movement, thus boosting the potential for growth and development.

Heightened safety
In workouts on a bench press machine there are a number of safety factors, which are still more important in doing decline bench press. There is no necessity to balance the barbell, which removes the risk of its falling on your face or pushing it off your ribs at the end of the eccentric contraction. Besides, there is no danger of pushing the barbell too far backwards owing to the fact that the exercise performing angle is fixed.
It should be noted however, that although machine bench presses are safer than the standard free weight lifting, there are still injury hazards if the exercise is not done in the right way. It is compulsory for the bodybuilder to choose reasonable weights and concentrate all his/her attention on safe and effective working with this very useful machine.

Basically, the rules for correct using of the bench press machine are the same as the ordinary free weight bench press exercises, excluding the above mentioned special features.

1.    Use slow contractions in doing the movements.
2.    Keep your elbows flung out.
3.    Put the accent on the chest muscles, not the forearms.