Tone is the speaker’s attitude toward the subject. A speaker’s tone is significant in a poem, because poems derive much of their meaning from tone. Although the tone is somewhat playful, it has an edge of the serious. This makes the poem powerful, because the reader is lured in and then given the message.
In the beginning of the poem, the speaker compares two possible endings for the world: Armageddon (fire) or hate (ice). Clearly the world will end one way or another! The juxtaposition of the different ideas and the use of simple rhyme make the poem playful. The topic is still somewhat serious, but the use of metaphors makes it a little more whimsical.
Yet when it is time for the speaker to share his attitude for the subject, the tone turns more serious. He mentions “desire,” which is a tense and powerful longing, and talks about if he were to “perish twice” it would be due to hate.
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice. (lines 6-9)
Hate, the speaker notes wryly, is just as dangerous as so-called Biblical Armageddon. People will destroy each other because they do not love each other.
So despite the poem's playful tone in the beginning, it packs a serious punch in the end that makes the meaning more apparent. The reader begins a playful poem, and then a moral is sprung- love one another, or the world will end sooner than you think.