Is trickle metaphor

Yes, "trickle" can be considered a metaphor when used to describe the gradual or slow dissemination of something, such as information, resources, or wealth. For example, when referring to the "trickle-down" effect in economics, it metaphorically illustrates how benefits provided to the wealthy are expected to gradually reach lower-income individuals. In this sense, the term evokes the image of a small stream or flow, emphasizing the slow movement and spread of a concept or resource.