I know that you all know the difference but sometimes it is useful to have a reminder.
Speaks for itself really.
So when I began to write Inceptus I set the start in Ireland with a man in position as a sniper in the rain. While visiting Ireland several years ago I experienced the 'soft Irish rain' and decided to use that in my description. On that occasion I used a metaphor describing the rain wrapping the man in its blanket. So saying that the rain is a blanket is metaphoric.
On the other hand if I'd said that 'the rain was as soft and warm as a blanket' - simile.
Okay - lesson over.
Peter May has written the Enzo Files a set of five books the first one being Extraordinary People.
I chose this book because I am reading it currently but I could have selected any of May's books as they are rich with such comparisons. In this one, at the beginning, he uses them to describe the atmosphere on a steamy, Paris evening in summer. If I'd chosen from the Lewis trilogy there are a plethora of examples describing the weather and the behaviour of the sea. The balance is good although at times he does indulge himself.
That balance is important and that is the key. There is little doubt that the use of such tools enriches the writing but overuse may reduce pace and induce boredom. There is no right or wrong number you have to have a feel for their employment, rather like having a feel for performing a piece of music.