The poem "Mother to Son" by Langston Hughes uses the extended metaphor of a staircase to represent life's struggles. A weary mother tells her son that despite facing many hardships in her own life, as represented by the broken stairs, she has continued climbing upward and urges her son to do the same - to persevere through life's difficulties and never give up. The poem conveys a message of determination in overcoming challenges through the mother's advice and personal example to her son.