Why is dancing wrong? God did not forbid dancing overtly in the Holy Bible. Many people danced (David, Miriam ... Aaron's sister...)
To be a Christian is to imitate the Lord Jesus Christ and follow His footsteps. In any situation we should learn to always ask ourselves 'What Would Jesus Do?" Our Lord said, "Take My yoke upon you and learn from Me" (Mt 11:29). Do you think if He were with us today would He dance?
Dancing is a worldly way to express fun and joy. We, as Christians should not conform to this world but be transformed by renewing our mind (Rom 12:2) and as St. John taught us "Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. For all that is in the world; the lust of the flesh, the lust of the eyes, and the pride of life; is not of the Father but is of the world. And the world is passing away, and the lust of it; but he who does the will of God abides forever" (1 John 2:15-17).
Unfortunately, many Christians justify dancing claiming that it is biblical, referring to David's dancing before the Ark of Covenant. This is completely different in motive, meaning and style from today's dancing. David's motive was to glorify God. He was playing religious music and singing psalms and hymns of thanksgiving praising the Lord "Then David and all the house of Israel played music before the LORD on all kinds of instruments of fir wood, on harps, on stringed instruments, on tambourines, on sistrums, and on cymbals" (2 Sam 6:5). David did not mean to dance for fun and earthly joy but it was a religious ceremony, a holy procession. "Then David danced before the LORD with all his might; and David was wearing a linen ephod. So David and all the house of Israel brought up the ark of the LORD with shouting and with the sound of the trumpet" (2 Sam 6:14-15). His style of dancing was "leaping and whirling before the LORD" is this the type of dancing we are talking about today and is it before the Lord? When his wife criticized his action, David answered "It was before the LORD, who chose me instead of your father and all his house, to appoint me ruler over the people of the LORD, over Israel. Therefore I will play music before the LORD. And I will be even more undignified than this, and will be humble in my own sight" (2 Sam 6:21-22).