Question

what is idiom and give me 20 examples for me

Answer 1

idioms are used to talk in a fancy and standard way.
at dead of night
logger head
at the eleventh hour 
at sixes and sevens
at the top of his voice
all and sundry
an axe to grind
above board

Answer 2

kicking a bucket
raining cats and dogs
pulling one's legs

going above the head
getting to the bottom of

going bananas
buttering some one up
a piece of cake

make one's blood boil
pain in the neck
making an  a s s of one self

rubbing salt on some one's wounds
needle in the haystack
take a back seat
taking cover

safe hands