Two short stanzas set a living creature against the people who destroy it. In the first, "the mad" turn a great green whale into oil. The word "mad" is blunt: it suggests the people doing this are driven by something like frenzy or greed. The title, "Whale light," makes the loss sharper, since oil from a whale is what once fed lamps. Something enormous and alive becomes a small, burning glow.
The second stanza shifts to something stranger and more tender. The whale's tongue "comes to dance / late and weary." Here the whale seems to be a body, not just material, and the dance reads like a last, tired movement, perhaps the animal's final gesture or a memory of it. The speaker doesn't shout or accuse. The restraint makes the poem feel quiet, sad, and a little eerie. It leaves you thinking about what gets burned away for the sake of light.