What is the surface area of a cube with side length 4?

To find the surface area of a cube, we use the formula: $6 \times$ (side length)$^2$. Substituting the given side length of 4 into the formula, we get: $6 \times 4^2 = 6 \times 16 = 96$. Therefore, the surface area of a cube with side length 4 is 96 square units. This concept is essential in understanding the spatial relationships in geometry and can be further applied to real-world scenarios.