It means something is difficult or dangerous to deal with for example:
- I never discuss about peoples religion it can be a hot potato.
2. “What you’re doing is as useful as rearranging deck chairs on the Titanic.”
This analogy indicates that if a person orders to perform a thing and the other person performs the opposite of what is indicated, then that action has no validity for the person who ordered.
A storm is to destruction, as an iceberg is to titanic. In this case, both speak to us of destruction.
3. His memory was very cloudy.
His memory is described as being very cloudy. If it is a cloudy day, then clouds cover up the sky and the sun for most of the day. So, this metaphor means that the man had a lot of hidden knowledge in his memory, or that he couldn't find or remember things very well
4. Her heart of stone was the result of the previous unfortunate events in her life
In this sentence, the heart is symbolized by a stone, emphasizing the lack of empathy she developed