One of the interesting ways that death is presented in this poem is that Thomas argues our death is not an actual "death" as such, or a cessation of being. Rather, he argues, our life force does not cease to be but returns to nature and therefore is found in nature in another object. The ending of this poem focuses on this belief by stating that our life force is connected to birds and flowers and other objects of nature. Consider the last four lines:
Though they be mad and dead as nails,
Heads of the characters hammer through daisies;
Break in the sun till the sun breaks down,
And death shall have no dominion.
Our life force therefore may enter something like a daisy and this of course supports the main point of the poem of Thomas, which is shown through the final line that is repeated throughout the poem: death, therefore, "shall have no dominion." Death equals a transfer of our life force rather than an ending of the spirit and soul that makes us tick, and our death means that our essence only enters nature.