You can use regular molecular dynamics to generate FEL, but Metadynamics is a more suited technique for enhancing sampling .

Thanks for your answer, Naveed.

As far as I know, for calculation of Free Energy or Gibbs energy particularly, you need to follow a procedure which utilize regular MD. Umbrella sampling, meta dynamic, thermodynamic integration, adaptive biasing sampling and so on. Based on your system, some of these may be more helpful and applicable. The idea behind each of these methods is to facilitate the sampling given the short time scale of the MD simulations.