From Jonathan Gardner's Korean Notebook
합니다 체 communicates a high level of formality, as well as humility or respect towards the listener. It is most appropriate in formal situations or with strangers.
Note that normally, imperative is avoided unless it is something the listener already intends to do. If you are trying to change someone's mind, then it's best to ask, "Will you ~ for me?" with the "해주시겠습니까?" question. This is formed by G + 주다 (to do ~ for someone else) + VS + 시다 (honorific infix) + VS + 겠다 (future tense) + VS + (스)ㅂ니까 (formal, respectful question).