* "He was a chicken about asking her out, afraid of rejection." (Here, "chicken" implies fear and cowardice.)
* "She was a real chicken when it came to heights, refusing to even look over the edge." (Again, "chicken" refers to fear, specifically of heights.)
* "He couldn't stand the pressure and backed out of the deal, acting like a chicken." (This compares the person's behavior to a chicken's tendency to run away from danger.)
Let me know if you'd like more examples!