The phrase "puts arm on" can have a variety of meanings depending on the context, but some possible antonyms for this phrase might include "removes arm from", "pulls away from", or "lets go of". Each of these antonyms suggests a different kind of action or motion, indicating a change from the original position of having one's arm in contact with something or someone. The opposite of "puts arm on" might also involve the use of different body language or nonverbal communication, such as crossing one's arms or standing at a distance. Ultimately, the antonyms for this phrase will depend on the specific situation and what actions or movements would be appropriate in that context.