Curiosity killed the cat
Excessive curiosity can lead to trouble.

A bird in the hand is worth two in the bush
It's better to hold onto something you have than risk losing it for something greater.

Let the cat out of the bag
To reveal a secret.

You can’t teach an old dog new tricks
It's difficult to change someone's established habits.

When pigs fly
Something that will never happen.

The early bird catches the worm
Those who act quickly or arrive early have an advantage.

A wolf in sheep's clothing
Someone who hides malicious intent under a friendly appearance.

Fight like cats and dogs
To argue or fight fiercely.

Monkey business
Mischief or deceitful activity.

Elephant in the room
A major issue that is being ignored.

Like a fish out of water
To feel uncomfortable or out of place.

Raining cats and dogs
To rain very heavily.

The lion’s share
The largest part of something.

Hold your horses
To wait or slow down.

To cry wolf
To raise a false alarm.

A snake in the grass
A treacherous or deceitful person.

All bark and no bite
Someone who threatens but doesn’t take action.

Like a deer in headlights
To be so surprised that you cannot move.

Kill two birds with one stone
To achieve two goals with a single effort.

The straw that broke the camel's back
A small burden that causes a large collapse.