The ad link the modal verbs the response words the interjection

A:
When I go to town now in Cardiff, I don’t know anybody.
B:
But, Richard, surely you’ve still got lots of friends here. (The speaker is asking for agreement with something that seems likely.)
Modality is about a speaker’s or a writer’s attitude towards the world. A speaker or writer can express certainty, possibility, willingness, obligation, necessity and ability by using modal words and expressions.
Speakers often have different opinions about the same thing.
These speakers are looking at the same thing.

Modal verbs

Here are the main verbs we use to express modal meanings:
Core modal verbs: can, could, may, might, will, shall, would, should, must
Semi-modals: dare, need, ought to, used to
Other verbs with modal meanings: have (got) to, be going to and be able to
See also:

• 
  Be able to
  
• 
  Be going to: form
  
• 
  Can
  
• 
  Could
  
• 
  Dare
  
• 
  Have got to and have to
  
• 
  May
  
• 
  Might
  
• 
  Must
  
• 
  Need
  
• 
  Ought to
  
• 
  Shall
  
• 
  Should
  
• 
  Used to
  
• 
  Will
  
• 
  Would
  

Modal words and expressions

There are a number of other words and expressions in English, apart from the main modal verbs, which also express modal meanings.
If you are learning English online, you probably already know there are many modal verbs in the English language. In this article, we’ll look at English grammar rules governing the use of the modal verbs must, have to, may, and might.
The first thing to remember about modal verbs is that, unlike ordinary verbs, they don’t change according to time (they have “substitutes” for this), and the main verb that follows them is used without the preposition to: can play, must pay, would go, etc.
These modal verbs in sentences themselves play the role of auxiliary verbs:

• 
  Can you swim?
  
• 
  Would you play?
  
• 
  May I go?
  

Modals Rules: How to Use Must, Have to, May, and Might
We’ll start with two common modal verbs: “must” and “have to.”