Fight Scenes and Action Scenes are, at their core, just like any other scene in many ways--especially when it comes to structure. They center around a basic yes/no question born from a character goal (based on something they care about or need), an obstacle keeping them from that goal, and an inevitable resolution that can be summed up as success, failure, or one of those combined with a complication.
Fighting and action involved mortal risk, so characters enter into a fight with strong motivation. Each character needs something or is fighting for something they care about. The character that approaches a fight or action scene with confidence and nonchalance or disinterest isn't interesting (unless he's about to learn a lesson about blind arrogance.)
Not only are goals in conflict, but also wills and personality. Once goals, consequences, and motivations are clear, let the fight first demonstrate who has the distinct advantage due to skill, numbers, position, etc. This continues until the other side is close to losing. Risk rises. Then, let the fight be about wills, needs, values, choice, risk and sacrifice. Who will sacrifice more? Who is more desperate? What choices do they make, and what do those choices cost?
The actions and events in the fight or action scene illustrate those motivations, choices and sacrifices. Personality and backstory add juicy detail and nuance to the unfolding choreography--a commando fights different than a housewife, but just as desperately.
When the action is resolved, not only is the story affected by the action or combat, but the characters will have been affected as well--usually one more than the others. What has the victor gained? What has the loser lost? What are the costs of their choices? What has been given up?
Writer of speculative fiction. Current work in progress is an untitled dark fantasy novella.