As you will have noticed, I am using this image as my 'avatar'.
The angel in this picture is singing.
In his hads, he holds a sheet with the lyrics of his song. We might question whether angels would need to read the lyrics of their songs from a sheet. After, all do they not eternally sing God's praises? Have they not memorised the words of their songs by now? Yet, perhaps there is no limit to what may be sung in praise to God. Perhaps singing of God's wondrous nature and works requires angels to ever be sining fresh songs in God's praise.
At the beginning of creation, the angels sang for joy. They watched as God created a new world and began a new work, bringing new glory to His name.
The angels sing of God's holy nature. We see in Isaiah, the Seraphim, the highest order of angels crying "holy, holy, holy, is the Lord of hosts, the earth is full of His glory."
The angels sing of our salvation. There is rejoicing in heaven when a sinner repents.
There is much debate about the elders in Revelation 5; are they the church, are they the redeemed of humanity or are they angels? Some contend that the song they sing proves that they are humans. Yet it appears from verse 8 of that chapter that the four beasts or Cherubim also join in the song:
And they sung a new song, saying,
Thou art worthy to take the book,
and to open the seals thereof:
for thou wast slain,
and hast redeemed us to God by thy blood
out of every kindred, and tongue, and people, and nation;
and hast made us unto our God kings and priests:
and we shall reign on the earth.
The salvation and glorification of man is the greatest and most wondrous display of God's glory and grace.
When the redeemed of the earth are in heaven in glory, they shall join their songs with the angels in praising the great Triune God.
Yet even now, we may praise God in our songs. We can have the confidence that when we sing, even though we do not see the angels, our celestial brethren, we are still in fellowship with them through our worship to God. As we sing on earth, they sing in heaven, delighting in the eternal goodness of God.
Notice that the angel, like in many other pictures, is barefoot. This displays his reverance toward God. Worshipping God is no light matter. It is the highest purpose for which we are created. So often our worship lacks reverance and respect. In many churches, music is used that is frivolous and shallow and does not truly honour God. In some churches, the music seems more designed to give glory to the performers than to God.
Yet even in churches which sing songs that are honouring to God there is no true reverance. Often worship is entered into as a ritual with little thought of what it truly involves. Often when I am presuming to worship God, my thoughts are on my own worldly cares and my own needs and desires. This is not true worship and is sin.