Anger comes from emotions. It is a reaction to an experience, and over time it becomes a pattern of response if the person does not change their environment or their response. Anger is a sign of a condition that needs to be changed, like nausea is a sign of food poisoning or pain is a sign of an injury. Anger is a sign of fear, of loneliness, of feeling abandoned or helpless, unsupported, unheard, misunderstood. It is frustration with your circumstances. It is tiredness, fatigue and sadness. It is the face of many underlying emotions that are not processed individually in their own channels.
Emotions are reactions assigned as translators of sensory events. Each person conditions themselves to react to different sensory events in whatever emotion they have normalized. Anger has the same structure and purpose as all other emotions. It can be a fast outburst or lingering feeling, loud or silent, projected outward or internalized. What we think of as an emotional response (especially one in anger) is often intense because, like a cup spilling over or pressure filling a balloon, the body reacts when it refuses to hold any more sensory input.
Emotional release is a time to experience yourself. The emotion defines your reality in a moment and narrows your perspective through that emotion. It allows you to block compassion, to prevent any other stimulation from entering, and to easily rationalize and assert your role in a situation. Anger gets a bad label because it is the response associated with hate, violence and arguments, and those often are seen as the causes of problems rather than reactions to unresolved problems. Hatred, violence and arguments can be driven by any emotion because they are results of perspective and uninterrupted patterns of emotional responses.
Anger is not useless or bad. It is an obvious sign that something is not right. It is a warning and opportunity to do something different for those who experience it in themselves and in others. All emotions are experienced in different ways and at different times because each person lives a unique combination of sensory events and has emotional response patterns specific to them. One person might respond by punching something in the same situation that another person might respond by crying and another might walk away and another might laugh. The responses are learning tools for being a human.