Anger is an emotion God gave us to enable us to move to protect ourselves or others from danger or harm when something hurtful or scary has happened. Anger is accompanied by a physical rush of adrenaline and other neurochemicals which impact us physiologically. Our senses are more acute, our muscles tense, preparing for action, and our facial expression and body language communicates to others to back off.
So, here is the important part to remember. Anger is always a secondary emotion that arises because of some kind of hurt or fear of being hurt.
–Melissa Haas, Emotions 101