Revelation 6  Jesus, the Lamb of God, takes the book and breaks the seals, one by one.  As each seal is broken, a judgement is issued.

As the first seal is opened, one of the living creatures calls out, "Come" and a white horse enters.  The rider has a bow and is given a crown.  He is sent out to conquer.   Our world is filled now with dictators and rulers, kings and presidents,  people of power and authority.. but this conqueror will bring them all down.  He will have authority to rule for a time and our world will be brought into subjection to him.
The second seal brings a second rider, this time on a red horse.  He carries a sword and incites war among men.
The third seal produces a rider on a black horse carrying a pair of scales.  This, we are told, indicates that famine will come to all the earth.
The fourth seal brings forth a pale horse and the rider's name is Death.  He is accompanied by "Hades".  "And authority was given to them over a fourth of the earth, to kill with sword and with famine and with pestilence and by the wild beasts of the earth." (v8)

Disaster upon disaster will come upon this earth, bringing God's fierce judgements to those who refused to repent and turn to God's freely offered salvation.  And this is just the beginning.

When the fifth seal is broken, John's attention is drawn to the  base of the altar.  "the souls of those who had been slain because of the word of God, and because of the testimony which they had maintained;"  were crying out to the Lord for Him to avenge the spilling of their blood.  But, the "number of their fellow servants"  who were "to be killed" was not yet completed.

The sixth seal is then broken and a world-wide earthquake erupts.  It makes the sun turn black and the moon turn red.  Even the stars  are affected by this great earthquake.  The sky itself splits and the mountains and islands of the earth move.  Every person on the earth will run and try to hide for they know that the "great day of their wrath", the wrath of God and of the Lamb, has come.
"Who is able to stand?"  they cry.   No one.  No one will escape the judgements of God.

Father in heaven,  I praise You for You are great and Sovereign above all of Your creation.  The past, the present, and the future are in Your hands and are not a mystery to You at all.  We understand so little, but what we do know is that You are a loving and gracious God.  You have chosen to show us mercy and grace by sending Jesus, the Lamb, who was slain to purchase us, those who believe, for You.  Thank You that we will not face Your wrath, but that we will come to You in worship, rejoicing at the great salvation that You have provided.  Father, I pray for my own family, for those who are still unbelieving, and ask that You will break through their hard hearts, shining Your light once again, bringing them to repentance, that they might also be saved.  I thank You for hearing this prayer.  You are Faithful and true.  Amen.