On the mission where you are back on the surface of Mars you will have your first opportunity to get this trophy. Your convoy gets attacked and Winters tells you to go destroy some bug pods. Before you venture off, make sure you have the magnet gun. There is a weapon machine by the vehicles in your convoy.
Now head off and down the path a bit, a tentacle will spawn out of the ground. Take your magnet gun and when the tentacle flings something at you, catch the debris and shoot it back at the tentacle.