If something is a piece of cake it is very easy to do.

Example of use:
My English exam was so easy. It was a piece of cake.


Image by Tracy Hunter

To talk turkey is to talk seriously and openly about something, especially something that relates to business.

Example of use:
OK, let's talk turkey and reach an agreement about the new employment contract.

This idiom might have its origins in America, from the time of the Pilgrim Fathers.

According to Robert Shook, in his book The Book of Why (1983, Hammond), the Pilgrim Fathers often wanted turkeys (for eating) when they traded with the American Indians and the Indians would greet them with the words 'You come to talk turkey?'

Image by Alan Vernon

If something is water off a duck's back, or like water off a duck's back, it has very little effect or makes no impression at all.

Examples of use:
1. You can't hurt me with your insults. They're water off a duck's back.

2. Carol is always getting cross with her son for being rude, but it's like water off a duck's back.

Image by John Haslam