When native English speakers speak, only certain words are stressed, while others are spoken quickly, or glided over. Why?
English is a stressed language. Unlike other languages, which devote equal attention to each word, English stresses only the content words (words which convey the meaning) and glides over the helpers (words without a semantic meaning).
Nouns, principal verbs, adjectives and adverbs are all content words.
Pronouns, articles, auxiliary verbs, prepositions, and conjunctions are the helper words.
Ex: We will arrive on Monday.
Emphasis is placed on the words in orange.
A good way to learn this is to read any paragraph in English stressing each and every syllable. (You will notice that the sound is almost robotic).
Next, read the same paragraph, only this time stress only the content words, and glide over the helpers. If you need to, underline the content words first. Don’t get too caught up in which is which if you are not sure.
The point is to become familiar with the flow of English and to improve your rhythm, pronunciation and reading skills.