A student sent me the following question:
Hi Simon. Can I use proverbs and idioms in IELTS writing task 2?
My quick answer would be no. Proverbs are certainly not appropriate for an academic-style essay, and the kind of idioms that many students learn (e.g. "In a nutshell") should also be avoided. Click here to read a lesson about proverbs and clichés, and make sure you don't use them.
On the other hand, some idioms are acceptable, and you probably use good idiomatic phrases without realising it (e.g. the key to solving a problem). To read a longer explanation about using idioms, click here. Read that lesson carefully, and be very careful with the type of idioms that you use.