A metaphor for fog is 'SOUP' (4 letters) and 'peasoup' (7 letters). SOUP is a liquid dish made from a combination of ingredients, usually vegetables, that are cooked in a broth or stock. Peasoup is a type of SOUP made with split peas, which are dried peas that have been split and hulled. Both of these terms can be used to describe fog, as it is a thick, dense, and often wet cloud-like mass that can obscure vision.