The song "My Best Girl" by UB40 is a heartfelt declaration of love and devotion to someone special. The lyrics express the desire to share the relationship with others and communicate the positive qualities and impact this person has had on the singer's life. The singer wants to tell their friends about this person and all the things they do for them, emphasizing that they are their "best girl" and will always hold that position. They describe this person as everything that is good and wonderful to them. The chorus repeats the desire to always be close to this person and offer support whenever they are in need. The singer feels a deep connection and comfort with this person, stating that they fit their heart perfectly and without them, their life would be incomplete. The overall message of the song is a declaration of love, commitment, and gratitude towards someone who holds a special place in the singer's life. It conveys the longing to always be by their side and the belief that this person is the best thing that has ever happened to them.