The song as a whole is about the book of Revelation. The song takes the perspective of the author of the book, John 'the Revelator', hence the title of the song. The lyrics take on an abridged portrayal of Jesus the Christ, drawing all of its influence from various (rearranged) passages throughout the Revelation. The lyrics, by line:
Had a dream I was alone...
John is on the island of Patmos, when he suddenly experiences a vision. (Revelation 1.9-10)
A vast expanse of complete unknown...
John sees in his vision the heavens. (Revelation 4.1)
Sea of glass so clear it shone / Like gold...
In the heavens, John sees, in front of the Throne of God, a sea of glass. (Revelation 4.6) He later sees the City of God, which he describes as being like gold, and clear as glass. (Revelation 21.18)
Then a voice like thunder clapped...
The voice of Jesus the Christ, speaking to John. (Revelation 1.10)
As a dead man I collapsed...
John is filled with awe and fear, and immediately bows to the ground in reverence. (Revelation 1.17)
"I am the first, I am the last / Now rise my son"...
Jesus speaks, displaying his identity with God; he then tells John to stand. (Revelation 1.8,17; 22.13)
Then behold ten thousand kings / And every creature worshiping / Every eye was on one thing / One man...
John has a vision of all creation Jesus, the 'one man'. (Revelation 5.8-14)
He's like a lion, like a lamb...
Jesus is symbolized as the Lion of the Tribe of Judah (Revelation 5.5), as well as the Lamb of God (Revelation 5.6).
As though slain he holds the plan...
Jesus, being the Lamb of God, has been sacrificed for the sins of the world. (Revelation 5.6,9) He approaches the Throne of God and takes a scroll from God's hand. (Revelation 5.7)
To make war and peace with man...
A description of the contents of the scroll, how it brings both catastrophe for the wicked and salvation for the righteous. (Revelation 6-8.1)
And reign on earth...
Jesus is seen as the ruler of the whole world. (Revelation 1.5; 12.5)
Holy, Holy, is the One / Who was and is, and is to come...
This is the liturgy of the heavenly host. (Revelation 4.8)
In a robe as red as blood / He comes forth...
The robe Jesus wears is red with blood. (Revelation 19.13)
Ride like lightning in the sky...
The only reference to come from outside of the Revelation. An allusion to Jesus' words regarding the Coming of the Son of Man. (Matthew 24.27; Luke 17.24)
On the war horse he draws nigh...
Jesus comes in judgment, making war upon the wicked, riding a white horse. (Revelation 19.11)
The same one we crucified...
Jesus, who was crucified on a cross, comes in judgment on those responsible for his death. (Revelation 1.7)
Will return again...
A summary of the above portrayal: this is the Second Coming of Jesus the Christ.
The song as a whole is about the book of Revelation. The song takes the perspective of the author of the book, John 'the Revelator', hence the title of the song. The lyrics take on an abridged portrayal of Jesus the Christ, drawing all of its influence from various (rearranged) passages throughout the Revelation. The lyrics, by line:
Had a dream I was alone... John is on the island of Patmos, when he suddenly experiences a vision. (Revelation 1.9-10)
A vast expanse of complete unknown... John sees in his vision the heavens. (Revelation 4.1)
Sea of glass so clear it shone / Like gold... In the heavens, John sees, in front of the Throne of God, a sea of glass. (Revelation 4.6) He later sees the City of God, which he describes as being like gold, and clear as glass. (Revelation 21.18)
Then a voice like thunder clapped... The voice of Jesus the Christ, speaking to John. (Revelation 1.10)
As a dead man I collapsed... John is filled with awe and fear, and immediately bows to the ground in reverence. (Revelation 1.17)
"I am the first, I am the last / Now rise my son"... Jesus speaks, displaying his identity with God; he then tells John to stand. (Revelation 1.8,17; 22.13)
Then behold ten thousand kings / And every creature worshiping / Every eye was on one thing / One man... John has a vision of all creation Jesus, the 'one man'. (Revelation 5.8-14)
He's like a lion, like a lamb... Jesus is symbolized as the Lion of the Tribe of Judah (Revelation 5.5), as well as the Lamb of God (Revelation 5.6).
As though slain he holds the plan... Jesus, being the Lamb of God, has been sacrificed for the sins of the world. (Revelation 5.6,9) He approaches the Throne of God and takes a scroll from God's hand. (Revelation 5.7)
To make war and peace with man... A description of the contents of the scroll, how it brings both catastrophe for the wicked and salvation for the righteous. (Revelation 6-8.1)
And reign on earth... Jesus is seen as the ruler of the whole world. (Revelation 1.5; 12.5)
Holy, Holy, is the One / Who was and is, and is to come... This is the liturgy of the heavenly host. (Revelation 4.8)
In a robe as red as blood / He comes forth... The robe Jesus wears is red with blood. (Revelation 19.13)
Ride like lightning in the sky... The only reference to come from outside of the Revelation. An allusion to Jesus' words regarding the Coming of the Son of Man. (Matthew 24.27; Luke 17.24)
On the war horse he draws nigh... Jesus comes in judgment, making war upon the wicked, riding a white horse. (Revelation 19.11)
The same one we crucified... Jesus, who was crucified on a cross, comes in judgment on those responsible for his death. (Revelation 1.7)
Will return again... A summary of the above portrayal: this is the Second Coming of Jesus the Christ.