Leo Metal Sonic is a Hedgehog / Lion Hybrid Robot, aka. "The Supreme Shapeshifter".
That's why he also has a tail. He specializes in Circus Performances.
He can change appearance into his 2nd Form: Liquid Metal Lionhog or his 1st form: Revell Aircraft Sonic (A Copied "Buddy" Form Skill, from his rival: Zeo Metal Zee)

The short story:

Metal Sonic builded by Dr. Golden in the meanwhile after the "questions and answers" event with Luigi in Maniac Mania "Different Dimension". As Fierce Forces new game has triggered, Metal Sonic got updated by Silent's "Player-On!" Mind and turned into hers "Realistic Imagination".
Now as the greatest creation of Dr. Golden "Prepare-Up!" he seek to hunt on Silent "Player-On!" and capture her for his Master.

Silent "Player-On!" once has summoned from hers Concord Bracelet:
Sentinel Martial Artist Sonic and he turned into his Super Form to protect her from the danger...
Leo Metal Sonic has gained this opportunity to copy the Skill and gain new Ability to change himself for a certain amount of time, but still into: Super Leo Metal Sonic.

His Forms in Fierce Forces:

1st Shape: Revell Aircraft Sonic ("Buddy" Form)

2nd Shape: Liquid Metal Lionhog ("Animal" Form)

3rd Shape: Leo Metal Sonic ("Robot" Form)

3rd Enhanced Shape: Super Leo Metal Sonic ("Charged Robot" Form)