Albert Barnes Commentary Job 38:35

"Canst thou send forth lightnings, that they may go, And say unto thee, Here we are?" — Job 38:35 (ASV)

Can you send lightnings?—This means that lightning is wholly under the control of God. So it is now; for after all that people have done to discover its laws and to guard against it, they have still made no advances toward a power to wield it, nor is it possible that they ever could.

Lightning is one of the agencies in the universe that is always to be under divine direction. However much people may harness wind, water, steam, and air for their purposes, there can still be no prospect that forked lightning can be seized by human hands and directed by human skill for purposes of utility or destruction. Compare the notes on Job 36:31-33.

And say to you, Here we are—The margin says, "Behold us." That is, we are at your disposal. This language is derived from the practice of servants presenting themselves at their masters’ call, saying that they stood ready to obey their commands. Compare 1 Samuel 3:4, 1 Samuel 3:6, 1 Samuel 3:9; and Isaiah 6:8.