Meanings
Usage patterns
〈人〉が大将になるfor someone to become the leader/boss
He finally became the leader of the team.
〈人〉を大将と呼ぶto call someone 'old chap' or 'boss' as a friendly nickname
The shop owner always calls him 'boss' in a friendly way.
大将を務めるto serve as the anchor (last competitor) on a team
He served as the anchor in the judo team match.
〈人〉を大将に選ぶto choose someone as the leader
We all discussed it and chose him as the leader.