Anger alone is not a sin. However, it can lead to sin. Matthew 5:21-22 says, “You have heard that our ancestors were told, ‘You must not murder. If you commit murder, you are subject to judgment.’ But I say, if you are even angry with someone, you are subject to judgment! If you call someone an idiot, you are in danger of being brought before the court. And if you curse someone, you are in danger of the fires of hell.” Jesus describes anger as murder. The intent is the same. Anger begins with a thought. That thought stirs a bitterness and hatred inside of you. Murder stems from the same feelings: anger, bitterness, hatred. Both anger and murder both come from these feelings.
You have to be careful when you experience anger. While it is not a sin, if it is not controlled and dealt with, then it becomes sinful. For example, anger with a family member can eventually cause a rift in the relationship that keeps you from communicating. Anger with someone that wronged you can cause ill feelings and resentment toward the person, and these feelings can lead to sin. So, give all of your angry feelings over to the Lord, and allow him to lead you.