Figurative Language in Poems: Do Not Go Gentle Into That Good Night

This poem is a villanelle as the last lines of each staza ("Rage, rage against the dying of the light" and "Do not go gentle into that good night") alternating is a characteristic of a villanelle.
The words "good night", "close of day" and "dying of the light" are all metaphors of death. The poet has chosen these words as they sound as if the person is dying peacefully. All the above phrases give the reader the impression that the person is dying slowly with the "light" "fading".
The words "blaze like meteors and be gay" are a simile of happiness. Earlier on in the stanza, the poet talks about grave men who are about to die who realise that they have been living a life of sadness and know that that they should be living a life of hapiness.