Everything that God has created is good and useful because God, in his goodness, has created them. God degrees that some of his creations have more value than others and they suppose to serve the human race and to give glory to God. Otherwise they become heavy burdens rather than privileges because it is used differently from the original ideas when God created them. It is a tragedy for society when leaders of the society are driven by ambition to accumulate material things for personal gain. Natural resources of the world are suppose to share not to store or be territorial and in some cases commodities are the cause of chaos and divisions rather than treasures.
The second level of valuable things is the human creations. They are created not to destroy life but to give comfort for and for protection of the human life. A lamp lit hidden is useless because it consumes oil and shows no light for the house. The metaphor is referring to personal talents which God has given to each of us. When we keep our talents for our own use and share with no one our talents become hidden treasures. God's gifts are given to us to share and if not shared they will be dulled.
Amongst God's creations the human race is the most important one. The highest valuable of things are personal talents. We need to develop them to their potential for the benefit for others and that is what God has intended us to do when God calls us into being. Some people's personal talents are hidden and they need motivation and advice from experts to discover hidden treasures and self worth. Talents are needed for self enjoyment and for contributing to a society in which that person lives. Some have more talents than others and our task is to find out our inert talents to develop. The more you find out about your own talents; the more you learn to know about your self- worth and the more you appreciate life and enjoy life more. Some have so much potential but have never lived up to it and it is misfortune and disgrace. It is very much like great pearls are buried in the ground. When God creates you God put in your heart some gifts for you to cultivate in life and make life worthwhile. We are all valuable and worthy in God's eyes because we are all God's children and God's creation is born out of God's goodness.
The metaphors salt of the earth and light of the word follow straight after the Beatitudes listed in Mat 5:3-12. It indicates that we need to live out the spirit of the Beatitudes because they help people around us to have a taste for Jesus, and help them also to see the light of Christ in us as Jesus said:
Let your light so shine before men that they may see your good deeds and glorify your father who is in heaven. v.16
Our good work becomes light for people to recognize that we live not for ourselves but for God who has created us and the cosmos.