To fix a wobbly metal railing, follow these steps:
Clean rust off the railing, particularly on the railing connectors and screws, using white vinegar and a clean cloth.
Check the anchoring screws or bolts at each deck railing post and tighten them using a power drill or ratchet if they're loose.
Replace any broken or worn post connectors to prevent added stress on the other anchors. Use GRK Rugged Structural Screws for standard pressure-treated decks and Caliburn XL Concrete Screws for mounting on concrete or stone patios.
Inspect post-to-rail brackets for any damage that could cause a loose railing section and repair or replace as needed.
Protect post hardware by attaching post skirts or post base covers to the bottom of the posts to prevent future problems from exposure to water, dirt, wind, and sun.