Because it is a comedy, this play doesn't weigh as heavily as some of Shakespeare's other works in a consideration of deep moral lessons. It is quite entertaining in a light and farcical way.
The play centers around various romantic relationships. Through various conflicts, romance is portrayed as complicated and subject to the whims of other influences—from fathers to meddling fairies. Hermia and Lysander are in love, but this relationship is forbidden by Hermia's father, Egeus, because he finds Lysander unsuitable. Speaking of his daughter, Egeus proclaims,
As she is mine, I may dispose of her—
Which shall be either to this gentleman
Or to her death—according to our law
Immediately provided in that case. (act 1, scene 1, lines 44–47)
Here, Hermia's father exerts his authoritative control over her, trying to force her to marry Demetrius. Hermia doesn't seem to have much say in the decision.
Romantic control is also subject to the whims of fairies and magic. Human emotions are easily manipulated through Puck's magical potion, and both Lysander and Demetrius end up proclaiming their love for Helena rather than Hermia. Helena is so shocked by this turn of events that she thinks they are making fun of her. After all, she has continually tried to win the favor of Demetrius, who has told her,
Do I entice you? Do I speak you fair?
Or, rather, do I not in the plainest truth
Tell you, I do not, nor I cannot love you? (act 2, scene 1, lines 199–201)
Although Demetrius makes his initial inability to love Helena quite clear, he is easily swayed by just a few drops of magic potion at the whim of a fairy. The power of the fairies to so completely sway human emotions and relationships seems to point to a lack of depth in the connections humans form with each other.
All of the romantic conflict in this play seems to point to a somewhat troubling moral lesson: The romantic relationships of humans are fickle and easily manipulated. Through comical conflicts, Shakespeare seems to be chiding humans for the ways in which they fail to demonstrate an unfailing and constant love for each other.