Chest flys mainly work the pectoralis major — your main chest muscle. They also involve the anterior delts (front shoulders) and triceps a bit as supporting muscles.

What they target

  • Primary: chest/pecs, especially the pectoralis major.
  • Secondary: front shoulders and arm stabilizers like the triceps.

Why people use them

Chest flys are good for stretching and squeezing the chest through a wide range of motion , which can help build chest size and improve the mind- muscle connection.

They’re usually done with lighter weight and controlled form so the chest does the work instead of the shoulder joints.

Quick form tip

Keep a slight bend in your elbows and avoid lowering your arms too far back, since overextending can stress the shoulders.

If you want, I can also tell you whether dumbbell flys, cable flys, or pec deck flys are best for chest growth.