Two short lines hold a startling clash. A man says "I love you," a phrase we expect to be tender, but he whispers it at the very moment the chains break the speaker's wrists. The word "broke" makes the pain physical and sudden, and it suggests the chains are not a gentle image of being bound but something that injures her as they give way.
The title, "Closure," adds an uneasy irony. Closure usually means peace or an ending that lets someone move on. Here the ending seems to come with violence, and the declaration of love sounds hollow, perhaps too late, or perhaps a kind of manipulation. The poem doesn't say which, and the speaker's own feelings are left unspoken, which may be the point: she is silent while he speaks. The mood is cold, tense and haunting. Because the poem is so brief, the shock of the contrast lingers long after the last line.