I.G.
I also just answered to another post about a strong willed child, however from your post your situation is quite different.
If I read this correctly your son is ALWAYS angry and always defiant. To me that is a red flag.
I have a strong willed child, but she is not angry, she is sweet much of the time and stubborn about getting what she wants at other times. Yes, sometimes that means a tantrum, even at 5 years old, but it is never anger, just frustration. She wants to please, it is just hard for her to unite her own impulse and wants with what is expected of her - and it takes her a while to get to the point where she will adjust her behavior.
Here are some questions I would ask myself: does this happen just at home? How is he doing in school, particularly with peers and teachers? How about other family members? Keep a diary and write down the moods that you see, when is he happy and relaxed (if ever), does he ever follow directions (yours or other's) or is he always defiant? What are the situations in which his behavior is better or worse.
I do not think that a child that is constantly angry, never or rarely really happy or relaxed is "normal" and that you should get counseling and discuss this with your pediatrician.
Good luck.