If you're looking for antonyms for the phrase "keeping arms length," the first ones that come to mind are "embracing" or "getting close." Keeping someone at arm's length implies a distance, both physical and emotional, while embracing means drawing someone in close.
Other antonyms might include "welcoming," "inviting," or "including," all of which imply warmth and openness. While keeping someone at arm's length might be appropriate in certain situations, such as maintaining professional boundaries, it can also create a sense of distance and distrust. By embracing or including others, we can foster stronger relationships and build deeper connections.