Difference Between Shall Be and Must Be (With Table)

A verb indicates the actions of a person. In English, verbs are of two types one is the main verb that describes direct activities of a person, and the other is an Auxiliary verb that describes the mood, tense, and aspect voice of a person. Auxiliary verbs are complicated to construct. These are of three types one is primary auxiliary verbs, modal verbs, and semi modal verbs. “Shall” and “Must” are modal auxiliary verbs. These verbs are combined with “be” verbs in different tenses to express intentions, futurity, advice, and others.

Shall Be vs Must Be

The main difference between “Shall be” and “Must be” is that “Shall be” is used to express future actions like possibilities, futurity, moral compulsions, and commitments, whereas “Must be” is used to express believes, obligations, to order someone, logical conclusions, necessity, and to advice. The phrasal verb “Shall be” is used in the future tense, and
“Must be” is used in present and future tenses.

Shall be is used to question someone. Shall be is used only with I and We subjects. Shall be is also replaced with “Will be” in some situations. “Shall be” is used mainly in Future continuous tense to express positive and negative sentences. “Shall be” is hard to construct and is used in written English than in conversation. “Shall be” has present participle as the main verb. The structure of “Shall be” is

Subject + shall + be + ing form (main verb) -affirmative sentence

Subject + shall + not + be + ing form (main verb) – negative sentence

“Must be” is used to advise, conclude, order, and suggest. Both “Shall be” and “Must be” are followed by present and past participles. “Must be” is formally used in English conversation. “Must be” is easy to construct and understand. The structure of “Must be” is

Subject + Must+ be+ present or past participle -affirmative sentence

Subject + Must+not+ be+ present or past participle -negative sentence

Comparison Table Between Shall Be and Must Be

Parameters of ComparisonMust beShall be
Tense‘Must be’ is used in simple present and future tense.‘Shall be’ is used in the future continuous tense.
Meaning‘Must be’ is used to express obligations, necessity, probability, to give the order and advice.‘Shall be’ is used to express futurity, possibility, suggestions, and commitments.
Subject‘Must be’ is used with any subject.‘Shall be” is used with I and We only. 
Contracted FormThere is no contracted form for Must. Must not plus be is written as Mustn’t be.‘ll be for Shall be and Shan’t be for Shall not be.
ExampleHe must be playing Cricket.I shall be late tomorrow.  

What is Shall Be?

Future continuous tense is used to construct a sentence that communicates about future actions at a particular time. “Shall be” is a modal auxiliary verb that helps to convey the emotions of a subject like futurity, suggestions, commitment, and willingness. It is usually used to question with I and We subjects. “shall be” is also being replaced with “will be” phrasal verb. “shall be” is used formally in communication. It is used mainly in written documents like policies, procedures, government or business plans, and others to indicate dedication. Some of the examples of “Shall be” usage in the future tense are

Affirmative Sentence

I shall be attending a meeting in Mumbai next week.

We shall be playing carom at this time tomorrow.

 Negative Sentence

I shan’t be at home tomorrow.

I shan’t be coming to your wedding next week. I am leaving for Hyderabad tomorrow. 

Shall be is not used to interrogate someone, Will be is used instead. Shall be is preferred only in written language mostly.

What is Must Be?

“Must” is one of the modal auxiliary verbs that are used in the present tense and future tenses to convey command, advise, suggest, describe beliefs, assumptions, and necessity. “Must” verb is used in any sense, but “Must be” is used either in present or future tense. Preset tense talks about current or general situations, and future tense talks about future actions. The phrasal verb “Must be” is followed by either present or past participle. “Must be” has a similar meaning to Have to. Have to is a semi-auxiliary modal that is used to convey obligations, necessity, and order. Some of the examples of the phrasal verb “Must be” are

Affirmative sentence

It must be freezing in Kashmir.

The Articles must be written as per guidelines.

Negative sentence

You must not be late for the party.

They must not be relatives.

Main Differences Between Shall Be and Must Be

  1. The Phrasal verb “Shall be” conveys emotions like willingness, commitments, intentions, and futurity. the phrasal verb “Must be” convey advice, order, obligations, necessity, and possible conclusions.
  2. “Shall be” is used in future continuous tense, and “Must be” is used in present and future tenses.
  3. “Shall be” is used with I and We subjects, whereas “Must be” is used with any subject.
  4. “Shall be” is rarely used in conversation. “Must be” is easy to use in conversations to express obligations.
  5. “Shall be” and “Will be” has the same features and usage. “Must be” and “Have to” has the same features and usage.

Conclusion

Modal auxiliary verbs like “Shall be” and “Must be” are used to add emotions to the sentences. A sentence has a subject, object, main verb, and one or more modal auxiliary verbs. “Must be” is used in the present and future tenses with any subject. “Shall be” is used in future continuous tense, usually with I and We subjects. Both “shall be” and “Must be” are used to express the probabilities, commitments. “Shall be” is rarely used in conversations, and hard to construct the sentence

References

  1. https://books.google.com/books?hl=en&lr=&id=NY8oAAAAQBAJ&oi=fnd&pg=PR1&dq=english+grammar+self+study&ots=78KXCPlE–&sig=E0sMYDCg53BxeqDbVu98Q-mmPKk
  2. https://www.uop.edu.jo/download/Research/members/Oxford_Guide_to_English_Grammar.pdf