The seven seals are not all opened before the return of Christ, however six of the seven are as the sixth seal is in fact the second coming of Christ. Revelation 20:5 tells us that the rest of the (wicked) dead were not resurrected until the 1000 years were over. It is at that point the seventh seal is broken. At this time we see something incredibly profound in the final revealing of Jesus’ character and authority.
The opening of the seventh seal is a silence in heaven for about half an hour, Jesus shows the wicked why He couldn’t save them and passes them their eternal judgement. All will see that Jesus was fair and just in His decision and the opening of the seals is concluded.
The four horsemen of the Apocalypse (1st 4 seals) bring about hardships on earth as the way is made before the 4th rider brings devastation upon the whole world as she falls into a time of great tribulation. Three seals remain as the fifth and sixth seal are broken during troublous times. Zechariah sees a vision of 4 horses that have the same color as he is told they represent the four spirits of Heaven that stand in the presence of the Lord of the whole world.