They stand up and rebel against the Lord and his anointed. They would not submit to the Lord.
Through out this arrogance, God sits in the heaven and is not affected by it. Those who plan evil can never affect God. The evil plans of men will not affect God's greatness. God let's those who rebel against him do so - until he speaks in his anger and terrifies them in his wrath. He has set his King on his holy mountain. God has anointed someone to be king. The King then issues a decree, "The Lord had promised him, 'You are my Son - this day I have begotten you'.
God had begotten the King as his Son. He did not adopt the King. He did not make the King. He begot the King. God then commands the King to ask and he will give the nations for his inheritance and the ends of the earth for his possession. This verse points to Jesus. He is the begotten Son of God. Therefore, God commands him to ask. Jesus being obedient, will ask the Father for the nations. And The Father will give it to him. Based on this, we believe that the Father has given Jesus everything.
God then promised that the King will break them mightily and destroy them completely.
After this follows an advice: Be wise O Kings and be warned or judges: Serve the Lord with fear, and rejoice with trembling.
The psalm warns people of the futility of rebelling against God and his anointed. Those who rebel will be destroyed. So it advices rulers to submit to God. The psalm ends with a blessing: Happy are those who take refuge in him.
This psalm tells us of the authority of God and those he chose. No one is stronger than God and his Anointed. No matter how much they plot against God, they will never win - because God is victorious and he is Almighty. Instead of fighting against God, we must come to him in humility. We were made to serve God and not to rebel against him.
Father, may I know where I stand before you. May I be able to submit to you with a joyful heart.