Jesus' death as the Lamb of God gained a victory over the satanic powers that are in opposition to God. The Lamb of God defeated Satan, sin and the power of the grave. That is the message of Revelation 5.
His supreme act of triumph was accomplished by shedding his own blood. Jesus won the victory over his enemies by sacrificing his life as the Lamb. Through this act He is worthy to return as the "Lion" to rule the nations.
He was numbered with the transgressors. For he bore the sin of many, and made intercession for the transgressors.....
Isaiah 53:10-12
10Yet it was the LORD's will to crush him and cause him to suffer,
and though the LORD makes his life a guilt offering,
he will see his offspring and prolong his days,
and the will of the LORD will prosper in his hand.
11After the suffering of his soul,
he will see the light of life and be satisfied;
by his knowledge my righteous servant will justify many,
and he will bear their iniquities.
12Therefore I will give him a portion among the great,
and he will divide the spoils with the strong,
because he poured out his life unto death,
and was numbered with the transgressors.
For he bore the sin of many,
and made intercession for the transgressors.
(New International Version)
That is what makes him worthy to open the scroll and reveal the message of the book of Revelation.
This lamb metaphor has a double image. It tells us that the slaughtered Lamb is coming a second time as the Word of God's wrath to demand the blood of all who deny him.
Revelation 6:15-17
15Then the kings of the earth, the princes, the generals, the rich, the mighty, and every slave and every free man hid in caves and among the rocks of the mountains. 16They called to the mountains and the rocks, "Fall on us and hide us from the face of him who sits on the throne and from the wrath of the Lamb! 17For the great day of their wrath has come, and who can stand?"
(New International Version)
Revelation 19:7-16
7Let us rejoice and be glad and give him glory!
For the wedding of the Lamb has come, and his bride has made herself ready.
8Fine linen, bright and clean, was given her to wear." (Fine linen stands for the righteous acts of the saints.)
9Then the angel said to me, "Write: 'Blessed are those who are invited to the wedding supper of the Lamb!' " And he added, "These are the true words of God."
10At this I fell at his feet to worship him. But he said to me, "Do not do it! I am a fellow servant with you and with your brothers who hold to the testimony of Jesus. Worship God! For the testimony of Jesus is the spirit of prophecy."
11I saw heaven standing open and there before me was a white horse, whose rider is called Faithful and True. With justice he judges and makes war. 12His eyes are like blazing fire, and on his head are many crowns. He has a name written on him that no one knows but he himself. 13He is dressed in a robe dipped in blood, and his name is the Word of God. 14The armies of heaven were following him, riding on white horses and dressed in fine linen, white and clean. 15Out of his mouth comes a sharp sword with which to strike down the nations. "He will rule them with an iron scepter." He treads the winepress of the fury of the wrath of God Almighty. 16On his robe and on his thigh he has this name written:
KING OF KINGS AND LORD OF LORDS.
Thus, Jesus tells us... 