The AdS/CFT correspondence is a popular method which allows us to study non-perturbative systems. We use the AdS/CFT correspondence to study a system of neutral mesons at finite temperature with external electric field. We consider the system in non-perturbative situation that constituent quarks of mesons strongly couple to each other. In order to understand the AdS/CFT correspondence, we will first discuss some basic result of type IIB superstring theory. Then we discuss the AdS/CFT correspondence and D3/D7 model. Calculations of D7-branes action can be matched to physical observables. We explain how shapes of D7-branes can describe the property of phase transition from stable mesons to melting mesons. The phase transition is analogous to metal/insulator phase transition. As external electric field is applied, we can calculate the conductivity and drag force of the system.
