Lysander is Hermia's boyfriend and he really wants to get hitched. Since Hermia's dad isn't having it, Lysander runs off with Hermia to elope. In the woods, he's drugged (by mistake) when Puck squeezes love juice in his eyes, causing him to love Helena until Puck finally gives him an antidote.
Lysander is a lot like Romeo, a character Shakespeare conceived around the time he wrote A Midsummer Night's Dream. Although Lysander faces some major obstacles in his pursuit of love, he's a hopeless romantic. The first time we hear about him, we learn that he's won Hermia's heart by giving her pretty knick-knacks and sweets, and has even serenaded her at her window "by moonlight" (1.1). (Hmm. Seems like we have the makings of a balcony scene here, don't you think?) Lysander also happens to be the most poetical of all the lovers:
Ay me! for aught that I could ever read,
Could ever hear by tale or history,
The course of true love never did run smooth. (1.1.134-136)
This is one of the most famous lines of the play, and for good reason. Lysander's declaration pretty much sums up the play's idea that lovers always face difficult hurdles on the path to happiness—whether it's a disapproving parent, rival lover, or some other obstacle. We're also interested in the way Lysander locates his love for Hermia in a long, rich "tradition." For Lysander, love is epic and the stuff of great literature and history. Check out what he says about the nature of love:
Or, if there were a sympathy in choice,
War, death, or sickness did lay siege to it,
Making it momentary as a sound,
Swift as a shadow, short as any dream,
Brief as the lightning in the collied night,
That, in a spleen, unfolds both heaven and earth,
And ere a man hath power to say "Behold!"
The jaws of darkness do devour it up.
So quick bright things come to confusion. (1.1.143-151)
Lysander clearly recognizes that lovers face a million obstacles and can be quickly separated by "war, death, or sickness." Lysander also knows that, even though love can be explosive, like "lightening," it's usually short-lived: "So quick bright things come to confusion." The idea that life and love are transient, by the way, is a major theme in Romeo and Juliet, where Friar Laurence says the following about Romeo's passion: "These violent delights have violent ends" (2.6.9).
When Lysander and Demetrius fight over the same girl (first Hermia, then Helena), Shakespeare pokes fun at tales of chivalric romance, where two knights in shining armor joust to determine who gets the girl. Most literary scholars recognize that Shakespeare borrowed from Chaucer's "The Knight's Tale," where Palamon and Arcite fight in a tournament over Emily, a girl they've both fallen in love with.
This brings us to our next point. After Puck sloshes the magic love juice all over the forest and Lysander and Demetrius go chasing after Helena, it's really hard to tell the difference between the two guys. As much as the lovers like to think that they are unique, Shakespeare basically tells us that all foolish young lovers are alike.