The speaker describes a person they love by comparing him to three things: a rose, a melody, and a poem. Each comparison holds a contradiction. The rose pricks the finger and draws blood, yet it is sweetly tempting. The melody haunts the speaker's dreams, yet it also calms and soothes. The poem sends them in circles and confuses them, yet it helps them understand life. Love here is never simple. It hurts and comforts at once.
The ending shifts the focus. However many ways the speaker has of looking at him, he stays "unmoving" and "unshifting," and that steadiness keeps the speaker strong. The mood is tender and a little uneasy, like someone admitting that the person they depend on can also unsettle them. The repeated "but also" gives the poem a back-and-forth rhythm, and the short final lines feel like the speaker settling into something solid and reliable.