As the book's title suggests, the idea of "leaning in" is central to Sandberg's arguments. At the most basic level, it's a metaphor for the kind of assertiveness and ambition Sandberg wants working women to practice. "Leaning" toward someone or something suggests engagement, interest, and confidence; it's the opposite of flinching or backing off, which Sandberg argues that women are too prone to do whether they're negotiating a raise or preparing for a family. As the book progresses, however, Sandberg begins to use the phrase in more unexpected ways, arguing, for instance, that men need to "lean in to their families" and expressing hope that her children will "lean in—all the way" when they "find where their true passions lie" (120, 172). "Leaning in," then, is ultimately a motif that Sandberg uses to develop themes surrounding personal choice and growth; it does not necessarily require ambition in the traditional sense, but it does require that people become the best possible version of themselves.

The jungle gym metaphor is one that Sandberg borrows from Pattie Sellers, but she also expands on it as a symbol for career success. The core idea is that advancement at work isn't necessarily a straight line; people may switch employers (or even lines of work), accept temporary "demotions" in exchange for other opportunities, or take time off to raise a family.