In the second line of this poem, the speaker claims that "old age should burn and rave at close of day." Here, he refers to people who have reached old age and are thus nearer to death than most, as "age" itself cannot do anything, and the word choices "burn" and "rave" imply that older people should fight against death loudly, forcefully, and with every bit of strength they have.
Typically, the word "rave" is associated with someone who is not in control of themselves; if someone is raving, then they are so angry or upset that they cannot hear reason or recognize anything other than their own feelings or perceptions. These connotations, nearing the prospect of insanity, help us to conjure up a visual image of an older person screaming and yelling, perhaps even waving their fists in righteous anger that death should come for them when they are not ready. Obviously, old people do not "burn," and so this word choice seems figuratively linked to the feeling of passion or anger, intense emotions that we typically associate with heat rather than cold. The connotations of "burn," in the sense of one's emotions, convey a similarly dramatic image, of one who is so angry and resolute that they would seem to be utterly and completely ruled by their feelings and empowered to remain alive a while longer by the sheer force of those feelings.