Property checking is also a part of Formal Verification.
Your statement : Formal verification is related to Functional Veriifcation
This can be true, but will give you a scenario where the above statement can be true.
Lets take you have implemented an algorithm for certain functionality and you have completely verified the functionallity with gate level simulation and good coverage of tests are done this algorithm written in RTL. But there was a change in requirement w.r.t Area/Speed. Now you implemented different algorithm keeping in mind of the same functionality.
Instead of running your new algorithm through Simulation, you can simply perform LEC on these oldd agorithm and new algorith. This way you have done functional verification of your new algorithm.
I hope you agree with my statements.