Metaphor

A metaphor describes one thing as if it were another, without 'like' or 'as', so that the qualities of the second are transferred to the first and the comparison is asserted rather than offered.

The meeting was a long corridor with no doors. The meeting is not a corridor, and the sentence says it is anyway. That assertion is what separates a metaphor from a simile, which says like a corridor and keeps the two things apart. Metaphor collapses them, which is why it hits harder and why it is easier to get wrong.

Two failure modes account for most of the trouble.

Dead metaphors. Grasp the point. Run the numbers. A flood of complaints. These were images once and are now just vocabulary. They are not errors, and hunting them all down produces stilted prose, but a page built entirely out of them has no pictures in it at all.

Mixed metaphors. We need to unpack this bottleneck before it snowballs. Three images, none compatible, and the reader sees the collision instead of the point. The test is literal: draw it. If the picture is absurd, rewrite.

A third and subtler problem is the metaphor that is doing the narrator no favours. In close narration, every image should be one that character could plausibly reach for — a farmhand and a naval officer do not notice the same resemblances — which is where metaphor stops being decoration and becomes show, don't tell.