Matthew 5:13-16 discusses how Christians are called to be "the salt of the earth" and "the light of the world" in order to shine God's light through good deeds. Just as a city on a hill or a lamp on a stand cannot be hidden, Christians should openly display their faith through actions so that others may see God's work and glorify Him. The passage calls believers to exist for a purpose beyond themselves and to serve through both their being and their deeds, bringing glory to God in all things.