Jesus is called God's Son all through the New Testament. However, while reading the scriptures, you will also notice that the title ‘Son of God’ is also used in reference to human beings, to angels, to the nation of Israel and to King David. So before we can say why it matters so much that Jesus bears this title, we have to see how it is used of everyone else, and then how His sonship differs from them all.

Let’s take a look at some of the Bible's references to the ‘Sons of God’.

Human beings in general are called ‘God's children.’ God created us and sustains us and as a human father provides for his family, God also provides for us, though much more significantly.

Acts 17:28 (NKJV)

for in Him we live and move and have our being, as also some of your own poets have said, ‘For we are also His offspring.’

The angels are called Sons of God because God sustains them and for their role in carrying out His commands.

Job 1:6 (NKJV)

Now there was a day when the sons of God came to present themselves before the LORD, and Satan also came among them.

The nation of Israel is called ‘God's son’ by covenant. When God redeemed Israel out of Egypt, He claimed the nation as His own son. Israel did not come to be as other nations did. God formed it by His own hand and bound the nation to Himself by covenant.

Exodus 4:22 (NKJV)

Then you shall say to Pharaoh, ‘Thus says the LORD: “Israel is My son, My firstborn.”’

King David was called the Son of God in the sense of his office — as God’s anointed representative on the throne.

2 Samuel 7:14 (NKJV)

I will be his Father, and he shall be My son.

It is clear that the phrase the Son of God is used for a variety of purposes. However, in every one of those cases the sonship is derived. Humanity is son by creation, angels by service, Israel by covenant, David by office. Each was made a son. But Jesus was not made anything. He is the Son by nature — the eternal Son who has always been what He is, of one being with the Father (John 1:1, 18).

And it explains why His sonship was so explosive to those who first heard Him claim it. In the first century, a son took up his father’s trade; a son’s work was his father’s work. So to call God His own Father was to say He did the Father’s work — to forgive sins, to give life to the dead, to judge the world. These are not things a creature does. Yet these are exactly the works Jesus claimed as His own. His hearers understood Him perfectly:

John 5:18 (NKJV)

Therefore the Jews sought all the more to kill Him, because He not only broke the Sabbath, but also said that God was His Father, making Himself equal with God.

Notice what they heard: not a lesser title, but a claim of equality with God — and they were right to hear it that way. Jesus did not correct them. He pointed them to the very same evidence:

John 10:37-38 (NKJV)

If I do not do the works of My Father, do not believe Me; but if I do, though you do not believe Me, believe the works, that you may know and believe that the Father is in Me, and I in Him.

The works prove the sonship — not the other way round. He does what only God does because He is what only God is.

Here, then, is the difference. Humanity is God's offspring in creation. The angels are God's sons in service. Israel was God's son in covenant. David was God's son in office. But Jesus is God's Son in being. The others bear the title; He is the title. That is the difference.