ZnO columns with different morphologies were grown on Au- and Cu-buffer layers deposited on Si substrates. This indicates that the metal buffer layer will affect the growth rates along different directions. The theoretical calculation shows that O atoms are favourably adsorbed on the hcp sites on both the Au (111) and the Cu (111) surfaces. However, the adsorbed Zn atoms are stabilized on the top site of the O atoms on the Au surface while they are favorable on the fee sites on the Cu surface. This suggests that the different morphologies initiate from the different adsorption sites of Zn atoms on the two metal surfaces.