By this time in the story of Job, he is probably regretting that he ever called out for an audience with the Almighty. Again and again, God has challenged Job to consider that his power and knowledge and understanding are severely limited. This theme continues in chapter 40.
We begin with a brief interlude where God addresses Job: "Will the one who contends with the Almighty correct Him? Let him who accuses God answer Him!" (vs. 2) Job, however, is not prepared for such a direct line of questioning. He recognizes his own unworthiness and covers his mouth in humility.
God then resumes his monologue. He points out to Job that his weakness and limited knowledge prevent him from understanding God. Human beings can neither adorn ourselves with glory and splendor nor save ourselves by our own right hand. It is God alone who is equipped to judge and punish.
As He begins to draw His speech to a close, God has in mind two exhibits that He specifically wants to draw Job's attention to. These two creatures represent the majesty of God's creation, and they are far above anything that human beings can master and control.
The first is the Behemoth, described in verses 15-24. Sometimes Christians like to play the fun game of "What do you think the Behemoth is?" My favorite proposal, and what I consider to be the leading idea, is the mighty hippopotamus, certainly an impressive beast by any standard!