Revelation often portrays single realities with dual, paradoxical images. In chapter four, thunder and lightning emanated from God’s throne, yet so did a glassy sea. God is not tame, yet He is full of shalom.
Now in chapter 5, God reveals a scroll with seven seals (1). Then an angel asks if anyone is “worthy” to break the seals (2). No one is found in all creation (3), and John weeps (4). But one of the elders (higher angels) tells John to stop weeping - Someone worthy has been found (5).
He is the Lion of the tribe of Judah, the most ferocious and dominating of the animals. And he is the Root of David, the great warrior king. This lion, this warrior King has conquered; thus He is worthy (5). That’s the first image.
Yet when John looks he sees not a Lion but a Lamb (6). Standing above the highest angels, before the throne, this Lamb appears to have been slain. At the cross, he both conquered all rebellion against God and also took it away from us, by taking it upon Himself (John 1:29, see also Isaiah 53:7). He is the Lion of Judah (Genesis 49:9), and the spotless lamb of God, given for us (1 Peter 1:19).
Thus the prayers of the saints are now brought before the throne (8). The way has been made, through this mighty Lion, who is the self-giving Lamb. Which is why new, glorious praise erupts around the throne (9-14).