General Intelligence:
* Sharp as a tack: Very intelligent and quick-witted.
* Bright as a button: Intelligent and lively.
* Quick on the uptake: Able to learn and understand things quickly.
* Have a sharp mind: Be quick and intelligent.
* A mind like a steel trap: Have a very good memory and be able to recall information easily.
* Have a good head on their shoulders: Be sensible and intelligent.
* Have brains in their head: Be intelligent.
High Intelligence:
* A whiz kid: A young person with exceptional intelligence or ability.
* Genius: A person with exceptional intellectual ability.
* A walking encyclopedia: Someone with a vast amount of knowledge.
* A brain trust: A group of highly intelligent people.
Specific Types of Intelligence:
* Street smart: Having practical knowledge and common sense about how to survive in the real world.
* Book smart: Having a lot of knowledge acquired from books and academic studies.
* Savvy: Having a good understanding of how things work and how to achieve success.
* Astute: Having or showing an ability to accurately assess situations or people.
* Perceptive: Having or showing a good understanding of people and situations.
Negative Connotations:
* Know-it-all: Someone who believes they know everything and is often annoyingly superior.
* Smart aleck: Someone who is overly clever and sarcastic, often in a way that is annoying or disrespectful.
Remember, the best idiom to use will depend on the specific context and the level of intelligence you want to convey.