Dr. Golden "Preparation":
That Wild Lynx has No Idea how many traps I have set!
Bring me Silent "The Player" here! Ha Ha!

Leo Metal Sonic: Right away, Master! Her chance of escaping from me, equals... Null!

Sonic "Tune-Up!":
*Thinks* Tsk... Ain't gonna be beaten by "animatronic" version of me! I'll prove, that the Clone is better than Robot! I'm the "Real Deal" after all! A superior than Original!

Fun Fact:
Leo Metal Sonic can shape a mouth on his face, because is made from a stable liquid metal
(which can change the consistency to, for example: sharp steel teeth)

Same goes for Zeo Metal Zee
(A Wolf Shapeshifting Military Robot, built by Silent "The Player/Avatar" and trained to protect her at all cost! Especially... before Leo Metal Sonic!)

This is in order to make their faces easier to express.

Just as Zeo Metal Zee can cheer up Silent "The Player/Avatar" and show his smile.
Leo Metal Sonic, on the other hand, can intimidate Silent for more effect for the meter of FEAR to grow up easier while the first challenge mode is activated.
As well as to Bite her to "Eat" the Stamina Core (After 7 Bites, Silent Can't use Items)

They don't have to do it in this Form, but they can if they want to.
Also they can talk, even without mouth.

*Spoiler* Most likely Leo copied this skill from Zeo.