The speaker addresses someone who seems impossible to keep or hold close. The opening lines imagine a woman with power so great that if she could truly bind or hold this person, she could do other impossible things: fasten fire to a wall or hold a waterfall in her hands. The third image deepens the idea—she could keep the wind itself from blowing on a warm spring night when the moon is low and bright.
Rather than describing a real person, the poem uses these graceful, impossible comparisons to say something about the beloved: he or she is as wild and fleeting as fire, water, and wind. The tone is not bitter, but wistful and almost admiring. There is longing here, but also acceptance that some people cannot be possessed. The short lines and soft nighttime imagery create a quiet, dreamlike mood, as if the speaker is sighing over an unattainable love.