Death is presented as a force which should be met with passion and energy, rather than acceptance. Thomas' message is that it is better to tackle life than accept death.
There is an innate frustration in the poem as Thomas is himself fighting the anger and fury at the imminent death of another, his father. It is possible that he is contemplating an approach to death which seems worthy of its finality. The poem advocates meeting death aggressively; with 'rage'. The rage seems to be directed at the diminishing 'light', implying that the anger is with the end of life rather than the beginning of death.
Thomas' treatment of the various types of men meeting death shows him to feel that he wishes all to fight until the end. The final stanza is deeply personal in being addressed to Thomas' father, and is torn between the positive and negative-
Curse, bless, me now with your fierce tears, I pray.
The oxymoron and alliteration within the phrase 'fierce tears' empitomizes the poet's clever condensation of the passion and drama of the passage from life to death, from everything to nothing.