Matching in NLP is your ability to match exactly the physiology of your client to gain rapport. It’s a natural ability for your body to be in synch with another important person in your life, so don’t worry about whether you think you’ll be acting like a monkey! I’ve written an article about matching and mirroring inside rapport here:
The difference between matching and mirroring is the same as if you looked into a mirror (mirroring the person as in mirror-image) and sitting directly behind someone (matching their physiology with yours).
Also see the Rapport section.
Matching in NLP