For Egyptians, the frog symbolizes birth, generation, water, renewal, and fertility. The Egyptians wear frog amulets and even have a frog-headed goddess named Heqet. With his staff, Aaron obeyes the Lord and summons frogs over the land of Egypt. He does so that Egypt will know that there is no one, especially no god, like Yahweh. Though the Egyptian religious sorcerers are able to conjure frogs of their own by their secret arts, they are not able to remove the frogs from the land. Since his sorcerers and gods (or goddesses) failed him, Pharaoh must entreat Moses to ask Yahweh. There is no one like the one true God.
God causes the frogs to die, and the land of Egypt becomes foul. The creatures that symbolize birth, generation, and life are put to death in front of all Egypt. Only God is Lord of life and death, renewal and the water. Heqet obviously has no real power.
Just as God predicted, Pharaoh hardens his heart again and will not let the Israelites go. God has more demonstrations to show that He is Lord not only of Israel, but of Egypt and the whole world.
In Revelation 16, John sees a vision of unclean spirits like frogs, doubtless referring to the frog plague, manipulate and bring the whole world against Christ. At this Armageddon, a battle I believe took place on the cross in the First Century AD, Christ wins life for His people and judges the nation, Jerusalem, that has been withholding it—proclaiming, “it is finished,” (cf. Revelation 15:1; 16:13-16; 17:1ff).