I am going to introduce my company and products to a potential customer

Please show me a sample of FORMAL introduction letter

Thanks a lot!

This sounds like homework because I don't believe anyone owning a company would have to ask how to do this.

There is a good resource you can use to introduce you to writing formal letters.
"Secretary's Guide to Modern English Usage", second edition, by Jean C. Vernes, revised by Carol M. Barnum, Ph. D. Published by Prentice Hall, NJ. c. 1991.

There are other texts you can look at by both authors. Jean C. Vermes also wrote, "Complete Book of Business Etiquette" and Carol M. Barnum wrote, "Prose and Cons: The Do's and Dont's of Technical and Business Writing".

Good luck.