Zephaniah is a Minor Prophet of royal blood who teaches us about the Day of the Lord. He uses it to talk about the consequence of sin for Judah. A remnant will be saved (The humble and the lowly), all through judgement of the wicked.
The truth is, our sins separate us from God. When we know better, and we still sin, we are accountable. God loves us, and he wants to sing over us. Understanding His character shows us His heart.