Looks like you are looking for the antagonistic pair. The muscular group that flexes the arm would be the antagonistic pair of tricep brachi and the brachialis.
The brachialis is a muscle in the upper arm that flexes the elbow joint.
which shoulder muscle allows you to adduct your arm
Palmaris Longus
Pectoralis major
The biceps brachii is the prime flexor of the arm.
A muscle which bends or flexes any part; as, the flexors of the arm or the hand; -- opposed to extensor.
-Flexion of the Arm -Flexion of the Forearm-Supination of the Forearm-Stabilization of the glenohumeral joint
break throw muscle shrug write
The teres major muscle is considered to be antagonistic to the teres minor muscle. The teres major muscle is a larger muscle located in the upper arm that works to extend, medially rotate, and adduct the arm, while the teres minor muscle is a smaller muscle that works to laterally rotate the arm.
Putting your arm down engages the triceps. The primary function of this muscle is to allow you to straighten your arm at the elbow. The tricep is the antagonist of the bicep.
It flexes the arm at the elbow.
the anterior part of the deltoid muscle flexes and medially rotates the humerus/ the arm. to do this it is helped by muscles like coracobrachialis and pectoralis major, corachobrachialis also adduct and flex the arm at shoulder joint.