A similie is an expression that is used when comparing something to a person or an object, with words such as ‘as’ and ‘like’’.  If you want to describe someone you know who is very shy, you could say that he or she is ‘as quiet as a mouse’.  Perhaps you have so many tasks to do in a short time at your work, so you could say ‘I have been as busy as a bee recently’. 

‘Like’ can also be used to make similar comparisons.  ‘My best friend can swim like a fish’ for example, means your friend is a very fast swimmer.  Do you sleep very deeply at night, so much that you don’t wake up if there is a sound?  Then you could say ‘I usually sleep like a log, especially after a long day at work.’

When it comes to metaphors though, they use everyday items or actions to replicate a meaning.  A classic example is to say ‘It’s raining cats and dogs at the moment’.  This meaning cannot be taken literally, but the amount of noise and commotion that cats and dogs make when together can be related to a heavy downpour or rain.  Another example can be with the sound of music.  When people hear beautiful music, it can make them very happy, which is why a useful metaphor can be: ‘When I heard about the changes that are about to happen, it was music to my ears.’

Similies and metaphors can be a good addition to your speaking when you want to compare or relate to something.  However, make sure you know how to use them correctly, with good pronunciation (i.e. the right intonation) and in the correct context. If not used properly, they can sound awkward, so make sure you understand them well before using them.  As they tend to be informal in their use, they may feel a little out of place in an academic essay, but for people who are taking the IELTS General Writing test, they can be a handy addition to an informal letter to a friend.