It could be argued that the initial relationship between Hermia and Lysander allows for the development of the theme of love. Hermia escapes from Theseus and her father because she is resistant to her father's insistence that she marry Demetrius. Understanding that, in the context of the play, refusing her father's demand could mean death, this act of defiance with Lysander does lend itself strongly to the theme of love.
However, the thematic presentation of love in A Midsummer Night's Dream is quite often one that shows love as being petty and dark. After the events in the forest, Demetrius and Helena are wed by Theseus and move on to enjoy a presumably happy marriage at the end of the play, completely oblivious to the fact that their affection for one another has been entirely manipulated by the fairies. Whether this is a happy or darkly bitter end for the two is left up to the audience.