Stabilizers are the long-key mechanism under space, shift, enter and backspace. On almost every stock keyboard they rattle. The rattle is the loudest sound the keyboard makes and a tiny amount of dielectric grease applied in the right two places fixes it almost entirely.
What to grease
Two surfaces matter: the wire ends where they meet the housing, and the stem channel where the wire travels. A small bead on each end and a thin coat in the channel is enough.
Reassemble, type for a few minutes, smile.