In addition to what Michael said about adverbs, I think that we emphasize the "be" verbs in spoken English by stressing them. By "stressing" I mean that we say it slightly longer and louder than the other words in the phrase. -You're not a native Spanish speaker, are you? -Yes I AM a native speaker. -I didn't see Khalid at the party. -Well he WAS at the party.

There is no comparable word for the verb "to be". You have to use an adverb, such as "really" (informal) or "indeed" (formal), which applies to the verb "to be" as well as the predicate of "to be". E.g. He really is a good student. He is a very good student indeed.