Destroy metal head beasts is a mission in Jak 3. Kleiver has scoped out a few metal head beasts moving through the Wasteland, so he ordered Jak to go and take them out, promising them they might find some new toys.
The PlayStation 3 and Vita versions of this mission are related to a trophy named "The Beast Beater", completing this mission will reward you with a bronze trophy.
Your first time using the Sand Shark. It is a lot faster than the Tough Puppy and has two forward-facing machine guns. The metal head beasts (four total) are very robust, large and speedy Metal Heads with a giant cannon on their backs which will launch an explosive ball from time to time. They run back and forth on a fixed path for this mission, so take your time to get behind them and shoot them down. As long as you get away before they hit you with their cannon or turn around and trample you, you'll be able to do this unscathed.
If you do collide with it head-on it will knock you into the air (causing the camera angle to change and time to slow down) and sending you flying. The actual collision does not deal that much damage, but depending on the length of the flight and the landing (a stone wall hits harder than sand) you can sustain severe damage to your buggy.
The last metal head beast will not be killed as easily as the others, however. When it collapses like the rest, it will stand up shortly after and continue on its path, forcing you to shoot it down again.