What is the metaphor in count on you song?

In the song " Count On You" by Bruno Mars, the metaphor used is being a "rock". The lyrics mention, " You'll always be my rock when I need you, I got you and you got me". In this context, "rock" is used metaphorically to represent steadiness, reliability and strength, which the singer can count on during tough times. Just like a rock provides a solid foundation, the person being sung to is a dependable and unwavering source of support for the singer,