Salt is a necessity of life and was a mineral that was used since ancient times in many cultures as a seasoning, a preservative, a disinfectant, a component of ceremonial offerings, and as a unit of exchange
Light is defined as life, as seen in John 1:4, “In Him was life; and the life was the light of mankind”. Those have faith through Him will have eternal life. This “life” is a gift Jesus brought from God into a dying world. Those who walk in darkness do not have eternal life because they don’t know God.
Both salt and light have properties which affect things around them. Salt is used to enhance flavor, and as a preservative. To 'be salt' means to deliberately seek to influence the people in your life by showing them the unconditional love of Jesus. Like salt in putrefying meat, Christians are to hinder social decay. Like light in the prevailing darkness, Christians are to illumine society and show it a better way. Light is a symbol used to mean awareness, knowledge, and understanding. To 'be light' means to be a witness to others concerning the truth of God's Word, especially about who Christ is and how he died and rose again for our salvation.