Paul McCartney's song 'So Bad' is a heartfelt ballad that delves into the emotional turmoil and longing one feels when separated from a loved one. The song captures the essence of yearning and the pain associated with missing someone deeply. Key themes include love, longing, and the bittersweet nature of relationships. Particularly poignant moments in the song arise when McCartney's tender vocals express the depth of his emotional state, making listeners empathize with the universal feeling of heartache.