This document discusses the importance and proper use of idioms in the IELTS speaking test. It explains that idioms can boost a test taker's score if used correctly but may lower the score if misused. Common idioms like "over the moon", "once in a blue moon", and "a piece of cake" are provided as examples. The document advises test takers to only use idioms they are 100% familiar with in context and to practice using them with a native speaker to ensure proper usage. Simply memorizing idioms is not recommended as inappropriate usage may seem unnatural to examiners.