We consider the ground state energy m (p, λ) for the classical nonlinear scalar field equationwhere N 3, λ > 0, 2 < p < 2 * and 2 * = 2N N −2 is the critical Sobolev exponent. It is well known that the equation has a unique ground state U p,λ in H 1 (R N ) such that U p,λ (0) = max x∈R N U p,λ (x). In this paper, we uncover a monotone property of m (p, λ) is fixed. For applications, we establish the existence and the concentration behavior of the least energy solutions (positive or sign changing) for the singularly perturbed elliptic equation with a variable exponent p(x):Our results show that the concentration behavior of the least energy solutions of the above equation is quite different from that of the semi-classical states of nonlinear Schrödinger equations with p being a constant: −ε 2 Δu + V (x)u = |u| p−2 u. Roughly speaking, for small λ, the least energy solution concentrates at the global minimum point of p(x), and for large λ, the least energy solution concentrates at the global maximum point of p(x).