Great poem, isn't it? Paul Fussell writes an excellent, long critical appreciation of it in his book "The Great War and Modern Memory", some of which is quoted at the site below. It's in far more depth than I can provide here, and it really is well worth reading. A copy of the poem (why haven't we got this on enotes?!) is also at the website below.
The poem is written in a very rough sort of trimeter (a line with three vague beats to it) which tends towards iambs. There are two stanzas, in unrhymed free verse.
The speaker, in the trenches, sees a rat as he picks a poppy to put behind his ear. He wonders that the rat is, in fact, more likely to live than he, and wonders what it thinks of its surroundings. He concludes that his poppy will die, but is safe for now, though a little white with the dust from the trench.
The poem works subtly through the interplay of symbols. The poppy - already associated with death and remembrance - echoes the blood of the dying men, as Fussell points out:
He is aware that the poppies grow because nourished on the blood of the dead: their blood colour tells him this. The poppies will finally fall just like the 'athletes'- whose haughtiness, strength, and fineness are of no avail.
Moreover, the white "dust" is not just literal: it also echoes men rotting into dust, as per the funeral service "dust to dust". The symbols are allowed to resonate, ominously. For more, visit the link, or post again here!