It is a challenge to synthesize clusters having a certain shape associated with a desirable property. In this study, we perform density functional calculations on ligand-protected Al(7) and Al(77) clusters. It is found that small ligands such as NH(2) Still prefer the compact structure of bare Al clusters. However, large ligands such as N(SiMe(3))(2) stabilize the experimentally observed shell-like structures due to the steric effect. This is different from the Ga(84) cluster case where small ligands can stabilize the experimental shell-like Ga(84) cluster. Our study suggests that the shape, and thus the properties, of clusters (for instance, C(3v) Al(7) cluster has a finite dipole moment in contrast to the centrosymmetric D(3d) cluster) can be controlled by using ligands with different sizes.