A Midsummer Night's Dream has such an extensive list of characters that one could probably write an entire book on the topic of your question. It would be impossible, in the space allotted, to give anything more than a shallow appraisal as to the characteristics of its major characters.
For one thing, when looking at the characters in this play, you should make a distinction between the Fairies and the humans. I'll discuss the Fairies first.
Within traditional folklore, fairies tend to be treated as dangerous and otherworldly, and Shakespeare certainly embraces this aspect of the mythology. His fairies are capricious and manipulative (Oberon and Puck certainly fit the trickster archetype with the way they manipulate the events of the play, shaping much of the play's action through their interference). Indeed, their manipulations and trickery extend not just over the humans, but also to one another (one can observe this in the side story involving Oberon and Titania and the enchantment that the Fairy Queen is placed under so that her husband can gain access to the child under her protection).
Meanwhile, there is the human world, which is depicted as a much more rigidly legalistic society than the capricious world of Fairy (a feature established in the play's very first scene). Among the human characters, we find Theseus and Egeus both standing for patriarchal authority. In contrast, there is Hermia (Egeus's daughter) and Lysander, who are passionately in love with one another and unwilling to sacrifice their relationship to bow before her father's authority.
Rather than submit to her father's choice, Hermia endeavors to flee Athens in order to marry the person she loves. Meanwhile, there is also Demetrius (also in love with Hermia, and her father's preferred choice of suitor) and Helena (in love with Demetrius). Among these four characters, I would say that one of the defining characteristics is passion. These four characters are all passionate, in love, and driven by their emotions. However, once the Fairies get involved, that same passion will lead to confusion and a great deal of emotional turmoil before their relationships are re-clarified later in the play.