The brachialis muscle is a muscle located in the upper arm. It is a large, triangular-shaped muscle located deep to the biceps brachii muscle. The brachialis muscle is responsible for flexing the elbow joint, which means it helps to bend the arm at the elbow, bringing the hand closer to the shoulder. This movement is important for activities such as lifting objects or bringing the hand to the mouth.

The brachialis muscle originates from the distal half of the anterior surface of the humerus bone, and inserts onto the ulnar tuberosity of the ulna bone. It is located deep to the biceps brachii muscle, and is surrounded by the brachioradialis and extensor carpi radialis longus muscles.

One example of how the brachialis muscle is used is when you lift a heavy object off the ground. To do this, you need to flex your elbow joint, which is facilitated by the brachialis muscle working together with the biceps brachii muscle. This movement allows you to grip the object securely and lift it with the necessary force.