Learn Turkish: Benim boyum iki metre.

In English, you say "I am two meters tall," describing yourself. In Turkish, you talk about your height as an owned object. Boy means "height" or "length," and -um is the possessive suffix for "my." So, Benim boyum literally translates to "My height is..." rather than "I am..."

Why is metre in the singular form if there are two of them?

This is a very strict rule in Turkish: any noun that directly follows a number must remain singular. Because you already used the number iki (two) to show plurality, adding the plural suffix -ler to make it metreler would be incorrect.

There is no verb like "is" at the end of the sentence. Is something missing?

It is not missing, just invisible! In simple "A is B" factual statements, Turkish often leaves off the third-person "to be" suffix (which would be -dir here). Saying Benim boyum iki metre is perfectly complete and natural for "My height is two meters."

Since this lesson is about kadar (as... as), how would I use it with boy to say "I am as tall as you"?

To make a comparison of equality with height, you place kadar directly after the person or thing you are comparing yourself to. Using this sentence's structure, you would say Benim boyum senin kadar (literally: My height is as much as you) or Benim boyum senin boyun kadar (My height is as much as your height).