''But at my back I always hear Time's winged chariot hurrying near'' illustrates

The lines "But at my back I always hear Time's winged chariot hurrying near" illustrate a metaphor. A metaphor is a figure of speech that compares two things without using the words "like" or "as." In this case, the speaker compares time to a winged chariot that is chasing him. The metaphor suggests that time is a relentless force that is always behind us, urging us to move forward and reminding us of our own mortality. The metaphor also creates a sense of urgency and tension in the poem, as the speaker feels the pressure of time running out.