Yes, muscle pairs work in opposition to one another. The lengthening of the biceps, for instance, shortens the triceps. That helps move your arm.
deltoid, pectoralis, trapz
pectoralis major dkfja
You cannot move your arm without using the muscle. Unless you use your other arm to move it. You may not be able to see the muscle move, but it must contract in order for the arm to move.
Deltoid is a muscle which is located in the upper part of your arm near the shoulder joint. It helps to move your arm upwards.
The Deltoid Muscle
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.
Well you have two muscles in your arm: the bicep and tricep. In order to make the arm move the two muscles must flex while the other extends and vice versa. So the bicep flexes and the tricep extends (the arm is bent). The bicep extends and the tricep flexes (the arm is straight)
Triceps help you raise the arm and biceps help you lower the arm.
voluntary, a typical person can move it at will.
They are a part of your body and your bones. And your arm bones also lead your arm and muscle to move.