A live wire
Definition 1 of 2
Pro Tip 1/3Colloquial Expression
Used in informal speech; not suitable for formal contexts. 
At the startup meeting, Jake was such a live wire, generating ideas.
Pro Tip 2/3Vivid Imagery
Creates a mental image of someone buzzing with energy. 
With her bright ideas and quick wit, Nora is a live wire in our team.
Pro Tip 3/3Personality Descriptor
Highlights a person’s dynamic and energetic traits. 
The new coach is a live wire; the players love his enthusiasm.