Holy, holy, holy is the Lord God Almighty, who was, and is and is to come.

Revelation 4:1-11
John saw the throne in heaven.
There are 24 other thrones surrounding the throne and seated on them were 24 elders.
Before the throne, seven lamps were blazing. These are the seven spirits of God.
In the center, around the throne, were four living creatures, and they were covered with eyes. The first living creatures was like a lion, the second was like an ox, the third had a face like a man, the fourth was like a flying eagle. Each of the four creature had six wings. Day and nigh they never stop saying: "Holy, holy, holy is the Lord God Almighty, who was, and is  and is to come."
Elders saying "You are worthy, our Lord and God, to receive glory and honor and power, for you created all things, and by your will they were created and have their being."
The scene and the perspective shift from earth to heaven.
The picture of the struggling churches fades before this sublime崇高 vision of the throne- the control centre of the universe- ringed by an emerald翡翠 rainbow.
The One who is seated there defies description. John can only say that he seems to be shot with diamond light, to glow red as a ruby.
Around him are the 'elders': possibly Israel's 12 patriarchs, plus apostles, but probably angelic beings who represent all God's faithful people.
Everything speaks of Gods power and glory, his utter faithfulness and purity.
Lightning and thunder speak of his awesomeness.
Four living creatures, all-seeing, represent the whole creation, ceaseless singing in honour of the almighty, the Holy One, 'who was, who is, who is to come.'
The elder join them to worship the eternal Lord of life.
Four living creature, similar, but not identical to Ezekiel's cherubim (Ezekiel 1 and 10) same as man, lion, eagle and ox or cherub.
Why?
The throne in the heaven is honor , glory and purity. He is the Lord Almighty, he is worthy to receive glory, honor and power.
John cannot describe the glory of the throne so he describe it seem like light of emerald, ruby and diamond.
The Lord who was, who is and who is to come. He is the everlasting God.
How?
Worship the Lord God Almighty!