We studied the effects of absorption and radiative decay rates of surface plasmon polaritons on the field enhancement in periodic metallic arrays by temporal coupled mode theory and finite-difference time-domain simulation. When two rates are equal, the field enhancement is the strongest and the peak height of the orthogonal reflectivity reaches 0.25. To demonstrate this fact, we fabricated two series of two-dimensional Au and Ag nanohole arrays with different geometries and measured their corresponding reflectivity and decay rates. The experimental results agree well with the analytical and numerical results.