The significance in the opening scene of Shakespeare's King Lear rests with two significant points. The first is that a central theme in the play will be reality versus appearance. In the first scene, Cordelia refuses to charm her father with flowery, empty words of love, but simply speaks the truth. However, her sisters do provide empty words of love and praise. This is what Lear wants to hear, but mistakenly believes the words are true. In doing so, he rejects Cordelia who truly loves him, banishing her from his life, and he accepts his other uncaring, deceitful daughters who will take what they can from him, and will not support him when he needs them most.
In addition, when Cordelia answers her father's question regarding her love with the word "nothing," Lear repeats the word "nothing" again. The idea of "nothing" foreshadows the "chaos" that will control the action of the remainder of the play; Lear will lose everything because rather than hear the truth of those around him and see things as they truly are, he chooses to be blind to what his eyes should see, and deaf to the words from those who care for him.
Ironically, where the King of France admires Cordelia's honesty, Lear in what Kent sees as madness, fails to notice the value of his daughter. By losing her, he loses all.
The opening scene is significant because in it King Lear enacts the decision that sets the entire action of the play in motion: he announces to his daughters that he is ready to retire and will divide his kingdom between them, giving the "largest bounty" to the daughter who can express the most love for him. His older daughters profess great love for him, but Cordelia, his youngest and favorite, refuses to flatter him. This enrages him. He banishes her and divides the kingdom between the two eldest, Goneril and Regan. By the end of the scene, we know from a conversation they have that these two daughters have lied to get the kingdom and don't have Lear's best interests at heart, thinking of him as infirm and lacking in good judgment.
The scene also is important in introducing us to most of the major characters in the play and giving us some glimpses into whether they are good or evil. It also introduces to Lear's tragic flaw: ironically the evil sisters are right that he shows poor judgment. He should not have given away his power while still alive and should not have trusted so much in people's goodness. Further, he shows that he can't discern between flattering words and true worth, banishing the honest daughter who would have treated him well in favor of lying flatters.