When I teach grammar in my ESL classes (at any level), I like to make sure that my students know the eight parts of speech (recognize the terms, that is) and how they function. What are they? Nouns, pronouns, verbs, adverbs, conjunctions/connectors, adjectives, prepositions, and interjections.
For Cambridge students preparing for any exam, it's essential that they have a consciousness of the parts of speech to make a sound choice of word to fit into gaps and clozes for the Use of English, Paper 3.
Native speakers of English also benefit from familiarity with the parts of speech. This cartoon series (which has been around for a long time, actually), The Schoolhouse Rock/Grammar Rock , is a fun way to learn and review these forms. Adverbs and adjectives color our speech and writing, and English would be pretty dull without them. Do take a few minutes to check out my favorites: one on adverbs and the other on adjectives.