The song 'Rainy Day' by America explores themes of reflection, melancholy, and finding solace in solitude. The lyrics convey a sense of longing and introspection, as the narrator contemplates the passage of time and the emotions tied to rainy days. The imagery of rain and nature serve as metaphors for emotional states and personal growth. Key moments in the song highlight the comfort and sadness intertwined in rainy days, making it a poignant reminder of life's bittersweet moments.