Welcome to the World of Modal Verbs!

In this chapter, we are going to learn how to use Modal Verbs to give advice, express necessity, and be polite. Modal verbs are like "mood setters" for sentences—they change the tone of what you are saying. Whether you are telling a friend which movie they should watch or explaining a rule that students must follow, modals are your best friends in English communication!

By the end of this lesson, you’ll know how to give great advice and use the right words for different situations, from casual chats to formal requests.


1. Giving Advice: Should vs. Ought to

When we want to give a suggestion or tell someone what we think is a good idea, we use should and ought to. For Thai students, these usually translate to "ควรจะ" (khuan-ja).

How to use them:

  • Should: This is the most common way to give advice. It’s friendly and works in almost any situation.
  • Ought to: This has the same meaning as "should" but is slightly more formal. Note: We always use "to" with "ought," but never with "should."

The Grammar Pattern (Active Voice):

\( Subject + should / ought \ to + bare \ infinitive \ (V.1 \ without \ 'to') \)

Examples:
- "You should study harder if you want to pass the exam."
- "We ought to save more water for the environment."

Quick Tip: The Passive Voice

Sometimes, we want to focus on the action rather than the person. The syllabus requires us to know the passive voice version too!

\( Subject + should / ought \ to + be + V.3 \)

Example:
- "The medicine should be taken after meals." (The focus is on the medicine, not the person taking it!)

Key Takeaway: Use should for everyday advice and ought to for a more formal tone. Both are followed by the base form of the verb.


2. Necessity and Obligation: Must, Have to, and Need

When advice becomes a rule or a strong necessity, we move up to must, have to, and need.

The Differences:

  • Must: Used for very strong advice or rules. It often comes from the speaker's own feelings (e.g., "I must stop eating junk food!").
  • Have to: Used for "outside" rules, like school laws or work requirements (e.g., "Students have to wear uniforms.").
  • Need: Used when something is necessary (e.g., "I need to drink some water.").

Grammar Patterns:
- \( Subject + must + V.1 \)
- \( Subject + have \ to / need \ to + V.1 \)

Common Mistake to Avoid:
Don't say "must to." Just say "must."
- Wrong: "I must to go."
- Correct: "I must go."


3. Being Polite: Requests and Offers

In Thai culture, we value politeness (ความสุภาพ). In English, we use specific modal phrases to make sure we don't sound rude when asking for help or offering it.

Asking for Help/Information:

Instead of just asking a question, use these polite formulas:

  • "May / Can / Could I...?" (e.g., "May I borrow your pen?")
  • "Would you please...?" (e.g., "Would you please explain this again?")

Offering Help:

  • "Would you like me to help you?"
  • "Can I help you with that?"

Softening a "No":

When you cannot do something, it is polite to use "softeners" so you don't sound harsh.

  • "I'm afraid..." (e.g., "I'm afraid I can't come to the party.")
  • "I'm sorry, but..." (e.g., "I'm sorry, but I don't have the information you need.")

Key Takeaway: Using "Would you please" or "I'm afraid" makes your English sound much more natural and professional (CEFR B1 level!).


4. Summary Table for Quick Review

Here is a quick guide to help you choose the right modal for the right job:

Function Modal Verbs Example
Advice should, ought to "You should rest."
Strong Rule must, have to "You must wear a helmet."
Necessity need to "I need to buy a pen."
Polite Request Could, Would you please "Could you help me?"

5. Don't Fall into These Traps! (Common Mistakes)

1. The "To" Trap:
Remember: Should, Must, Can, Could, May are NEVER followed by "to."
- You should to sleep. (Wrong!)
- You should sleep. (Right!)

2. The "S" Trap:
Modal verbs never change their form. They don't need an 's' even if the subject is He, She, or It.
- She shoulds to go. (Wrong!)
- She should go. (Right!)

3. Confusing Must and Should:
If you tell a friend "You must see this movie," you are being very forceful! If you just want to recommend it, use "You should see this movie."


Quick Check-up:

Try to fill in the blank: "The classroom _______ be cleaned every evening." (Hint: Use should in the passive voice).
Answer: should be

Good luck with your studies! Remember, giving advice is all about choosing the right level of "strength" and staying polite!