Protesters formed 'a human chain' [=they stood next to each other with their arms linked] around the ancient tree to prevent it from being cut down.
In the United States, the President as the commander in chief is at the head of the military 'chain of command'.
I thought he really won the lottery but he was only 'pulling my chain'. [=he was only playing a joke on me]
(..) One, seeing herself years older would put her into shock, and she'd pass out... ...or two, the encounter could create a time paradox... ...and cause a chain reaction that would unravel... ...the space-time continuum and destroy the entire universe! Granted, that's a worst-case scenario. (..)1989 Back to the Future Part II
(..) This is heavy. It gets worse. Your daughter tries to break him out and gets sent up for years. My daughter. I have a daughter? This one event starts a chain reaction that completely destroys your entire family. Doc, this date... This is tomorrow's newspaper. Precisely. I already went further ahead (..)1989 Back to the Future Part II