The metal jacket is an enemy in Jak II and Jak 3. It is a small, flying, insectoid metal head, closely resembling a wasp (hence being named after the yellow jacket). Metal jackets made their first appearance flying through the rift gate in the opening cutscene of Jak II. They were later seen at the strip mine in the mission "Rescue Vin at strip mine" during Jak II. They made a reappearance in Jak 3 in the mission "Find satellite in volcano" at the Great Volcano, where they were then found at the Monk Temple in the mission "Complete Monk Temple tests" shortly afterwards.
This metal head closely resembles a yellow jacket, hence the name "metal jacket". It has various bio-mechanical features common to the Metal Head species. It has a small insectoid head, with four very small eyes surrounding it's small skull gem. It has a small main body held up by a pair of gossamer wings with two very small arms. It has a tail almost three times the length of its torso, ending in a sharp metal point acting as a Blaster which can fire dark eco projectiles.
The metal jacket will shriek upon spotting an enemy, and then fly out and hover right in front of it. It will stay there, repeatedly firing dark eco projectiles until it is shot down. When it is destroyed, it will shriek again, and it's skull gem and dark eco droppings will automatically come to Jak (opposed to him travelling to pick it up).
Metal jackets attack by launching a dark eco projectile which flies in an arc towards it's target, although in Jak II they primarily do this as at a long range, where they instead close the distance and fly close to their target in Jak 3. Nonetheless they remain easy to avoid, as long as you don't stand still long enough for them to aim and hit you.
You will need at least two shots with the Blaster to kill these, which means that after the first shot you will have to aim again as the first one will knock them away. This is not a problem in Jak 3 if you use the Beam Reflexor where the reflected shots practically do the work themselves.