I could eat a horse: This is an idiomatic expression. You must use ‘COULD’ (NOT can) when you don’t really mean what you say. We don’t mean that one will eat a horse, it is an exaggerated statement. The following situations relate to ‘NOW’ (i.e. present situations)
- I could eat a horse! (i.e. I am so hungry and I feel like eating a very large amount of food.) -(present)
- He is so angry with her. He could kill her! ( i.e. present)
- He could beat me! (i.e. He has lost his temper so anything may happen unpredictably)
- The MD is in a very angry mood. You had better not put up the request now. He could shout at you!
- He is so tired. He could sleep for a week!
When we want to convert the above examples into the past the following structural changes will take place:
(Could have + past participle of the verb)
- I could have eaten a horse! (i.e. I was terribly hungry, maybe after a tiresome trekking)
- He was so angry with her. He could have killed her! (past – actually he felt like doing anything like killing her, but he didn’t do so)
- He could have beaten me! (i.e. he was in such an angry mood)
- The MD could have shouted at me! He was in a very bad temper.
- He was so tired. He could have slept for a week! (Maybe after a long trip – a past situation)