The most obvious theme you could explore when writing your essay is that of a continuing class struggle, even 800,000 years in the future. As the Time Traveller overlooks the future Earth he notices that the individual family has disappeared and presumes this society to be a form of communism. This theory is disproved when our hero is introduced to the Morlocks, but we can then begin to see obvious distinctions between the Haves and the Have-nots. Even in the names of the two species we can notice discrepancies. The word Eloi itself sounds like the word 'elite,' describing a rich, elite being, while Morlocks is a seemingly perfect word to describe a brutish, ape-like creature. So even in the future Karl Marx’s theory that “all history isa history of class struggle” remains pertinent.
"The Time Machine" is Wells's Socialist warning of what will befall mankind if capitalism continues to exploit workers for the benefits of the rich. If your essay is about the themes explored then you might look at the following
evolution and social Darwinism
the white sphinx
time and relativity
you could also refer to
Chris Semansky. "The Time Machine: Essays and Criticism." Novels for Students. Ed. Marie Rose Napierkowski. Vol. 17. Detroit: Gale, 1998. eNotes.com. January 2006. 15 February 2010. .