A popular option in most gyms, the machine bench press targets the same muscles as the free weight bench press alternatives, but is often a safer option for beginners and those lacking strength and experience.
The primary target of the machine bench press is the chest, with the anterior head of the deltoid (front region of the shoulder) and the triceps (muscle located to the back of the arm) assisting. As a general rule of thumb, the more the athlete tucks the elbows towards the torso during the bench press, the more the emphasis will be placed on the triceps and away from the chest. So, to target the chest, the upper arms should be just shy of perpendicular to the torso throughout.
Once a reasonable level of strength and experience has been gained, it is recommend the athlete moves onto the free weight alternatives, namely the barbell and dumbbell bench press.