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]
(..) I wanted to ask you a question. How would a predator... ...track a reptile? Oh, they don't. Most reptiles are at the top... ...of their food chain. Kings of their domain. They gotta have vulnerabilities. Why the sudden interest in the cold-blooded? Just asking a question. (..)2012 The Amazing Spider-Man