11 Then I saw heaven opened, and there was a white horse. Its rider is called Faithful and True, and he judges and makes war with justice.
Heaven opened, most likely refers to a literal sky as people will see Him.
The white horse mentioned here is different from the one spoken of in Revelation 6. The rider is called Faithful and True which points to two verses
Jesus told him, “I am the way, the truth, and the life. No one comes to the Father except through me.
1 Corinthians 1:9
God is faithful; you were called by him into fellowship with his Son, Jesus Christ our Lord.
Jesus is the one who is faithful and true.
Jesus’ judgment upon the wicked is justified and righteous because He is the standard of good and those who are opposed to righteousness will be condemned.
12 His eyes were like a fiery flame, and many crowns were on his head. He had a name written that no one knows except himself.
For further study on Jesus’ appearance click: Revelation 1:11-15
Many crowns were on his head refers to being Lord of lords and King of kings
He had a name written that no one knows except himself. Scripture doesn’t say why He is keeping His name from anyone but it might be for those who will go to be with Him in heaven.
The name that He is keeping confidential might reflect a characteristic of Jesus not yet known to men.
13 He wore a robe dipped in blood, and his name is called the Word of God.
A robe dipped in blood refers to His sacrifice on the cross for humanity.
His name is called the Word of God, it reveals that everything that comes from Jesus’ mouth is God-breathed. It also reveals His deity as Creator of the universe.
Then God said, “Let there be light,” and there was light.
In the beginning was the Word, and the Word was with God, and the Word was God. 2 He was with God in the beginning. 3 All things were created through him, and apart from him not one thing was created that has been created.
14 The armies that were in heaven followed him on white horses, wearing pure white linen.
The armies are in reference to the saints of all times that ever lived will come with Christ at His second coming.
1 Thessalonians 3:13
May he make your hearts blameless in holiness before our God and Father at the coming of our Lord Jesus with all his saints. Amen.
Wearing pure white linen means righteousness that is only attained through faith in Jesus Christ.
15 A sharp sword came from his mouth, so that he might strike the nations with it. He will rule them with an iron rod. He will also trample the winepress of the fierce anger of God, the Almighty.
When Jesus and His army face the antichrist and his forces, with a spoken word He will kill and defeat His enemies.
He will rule them refers to Jesus’ millennial reign.
Iron rod shows that His rule on earth is supreme.
He will also trample the winepress of the fierce anger of God, could mean His judgment (the sword, His spoken word which will cause their death) will come upon the nations that fight against Him with the antichrist as their leader.