Sacramento Kings forward Chimezie Metu was so pissed after being fouled during a summer league game Sunday ... he threw a wild punch that connected with his opponent's forehead.
The fight all went down in Sacramento's game against the Dallas Mavericks in Vegas ... when Eugene Omoruyi collided with Metu while the Kings player was going up for a dunk attempt.
In the broadcast footage from the arena, you can see Metu was so upset after being knocked into ... he cocked back his right hand and violently punched Omoruyi in the face.