Thunder Guard is a move used by Sonic the Hedgehog that has only appeared in Sonic the Hedgehog (2006) as one of Sonic's Custom Actions. It is a move that gives Sonic a small Magnetic Shield. It can only be used after Sonic obtains the Yellow Gem.
When using this move, a shiny yellow Magnetic Shield with electrical surges forms around Sonic. While the Thunder Shield is up, Sonic attracts nearby Rings and he can withstand one hit from enemies, spikes and some other level hazards (excluding flames) without taking damage. However it cannot protect Sonic from falling into the bottomless pits. Also, after blocking damage once, the Thunder Shield will disappear, though it can be restored by pressing the trigger button again.
- When the Thunder Guard has been activated, it will remain active, even when the player changes the Yellow Gem Level Up Item to another.
- In the multiplayer mode, finishing White Acropolis while Thunder Guard is active causes the shield bubble to glitch and stay in the location where the player touched the Goal Ring.