Metaphor
Metaphors are statements which aren't meant literally, but instead imply some connection or comparison between the description and the thing described. In Lojban, metaphors can be formed in many ways, and can fall into two categories - sentences which can be interpreted literally but are not intended as such, and sentences which have no literal interpretation. This page documents some of the types of metaphors you may run into in the wild.
Simple Metaphors
Simple metaphors are where a small comparison is drawn between the subject of a sentence and the description, and context provides a way to see what is being referred to. Some simple metaphors may be marked with pe'a to call attention to the fact that a non-literal reading is expected. For example a software developer might be told ko cikre lo pe'a do bersa as a way to instruct them to fix their program, which is obviously not a literal son of theirs.
Cultural Metaphors
Cultural metaphors are metaphors which draw on the culture of the speaker or listener to provide meaning which is otherwise absent from the sentence and context. It's generally recommended that cultural metaphors in particular be marked with pe'a to call attention to the non-literal meaning, as these metaphors don't provide an easy way to understand them without the cultural background, but of course such marking is not required.
Sumti Lowering
Sumti raising is where the word tu'a is used to permit a concrete object (like a door) to be used where an abstraction is expected (like an action to be tried), permitting sentences like ko troci tu'a lo vrogai to be used, allowing the listener to infer the intended abstraction from context.
Sumti lowering is the opposite, where an abstraction is used in a place that a concrete object would otherwise be expected. This results in a sentence which has no literal interpretation, but which may provide a good comparison for creating a mental image. For example, the sentence mi jersi leka melbi fa lo mi se finti (translated as "I chase after beauty in my works") seems to capture the struggle of being an artist; as the speaker moves closer to the goal of beauty, the standard for being beautiful moves away.