I have a couple of metaphors of my own for Scrum.
For Organisations: Scrum is a Bulldozer
For an organisation with a reluctance or resistance to change, Scrum’s strict rules and clear identification of impediments provide the organisation with a mechanism to quickly see and remove obstacles that are wasting time and money, and sapping staff morale.
For Teams: Scrum is The Stabiliser Wheels on Your First Bike
For a team that is new to agile development, or working within an organisation that has never tried it before, Scrum’s simple principles provide a framework within which a team can and will have to learn mature engineering practices like Test-Driven Development, Pair Programming, Refactoring which make iterative software development not just possible, but a real pleasure. From the outside, management should find the team’s straightforward, easy-to-grasp progress reporting safe enough to let the team self-organise and learn the confidence and empowerment that every great team needs to succeed.
What happens when you take the stabiliser wheels off? Maybe something like this?