We know Jesus as the baby in a manger, as teacher, friend and even as sacrifice. In this passage we also see Jesus as he will be at the end: King of Kings and Lord of Lords. He will be the righteous judge of all of us. We also see that he is God's word (like in the beginning of John's Gospel). THe image of Jesus on a horse with a sword coming from his mouth is certainly strange, but God's word is often described as a sword because it judges and slices through all the lies we tell ourselves.
As we saw before, Jesus is stronger than all the powers of the earth. The kings and other powerful people might try to fight against Jesus, but they will never win. The good news is that even though Jesus judges, he judges like he lived: with righteousness and love.