Do flies build your chest?

The fly machine is ideal for increasing chest strength and muscle mass by targeting the pectoralis muscles. You have two sets of pectoral muscles on each side of the front of your chest: the pectoralis major and the pectoralis minor.

Are chest flys better than bench press?

Most research finds training with greater ROM stimulates greater muscle growth. That’s likely due to 2 reasons, but only 1 is relevant here. First, using full ROM can stimulate more stretch-mediated hypertrophy. However, flys actually achieve greater a greater pec stretch than bench presses.