A black Arabian named Balthazar brought myrrh, the bitter gum resin valued for its medicinal properties. They had come prepared. Knowing that it was the birth of the King, they had brought gifts to give to Jesus. Their desire was to lay the gifts at the feet of Jesus, and to worship Him. These gifts had significance.
Gold is the gift for a king.
The custom was that no one could ever approach a king without bringing a gift. Gold, king of metals, was the perfect gift for the king of man. Frankincense is the gift for a priest. The function of a priest was to open the way to God for men. Jesus is the only way to the presence of God.