1. Lesson Overview
In this lesson, you will learn how modal verbs combine with passive voice. Modal verbs such as must, should, may, might, can, and could often appear in passive constructions, especially in instructions, formal guidelines, academic writing, and scientific descriptions.
These structures allow speakers and writers to emphasise actions, processes, or requirements, rather than the person performing the action.
The passive form with modal verbs follows a clear structure:
modal + be + past participle
By the end of this lesson, you will be able to:
-
form passive constructions with modal verbs
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recognise how modal passives express obligation, possibility, and necessity
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understand how modal verbs modify the meaning of passive sentences
-
avoid common mistakes in modal passive structures
2. Concept Introduction
Consider the following sentences:
Active:
Researchers must follow safety procedures.
Passive:
Safety procedures must be followed by researchers.
Another example:
Active:
The team should complete the report today.
Passive:
The report should be completed today.
| Active Sentence | Passive Sentence |
|---|---|
| must follow | must be followed |
| should complete | should be completed |
Modal verbs remain unchanged, but the main verb becomes be + past participle.
3. Core Explanation
Passive constructions with modal verbs follow the structure:
modal + be + past participle
Example:
Active:
The team must complete the experiment.
Passive:
The experiment must be completed by the team.
Example:
Active:
Scientists may discover new evidence.
Passive:
New evidence may be discovered by scientists.
In these sentences, the modal verb expresses meanings such as:
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obligation
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possibility
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permission
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recommendation
while the passive voice emphasises the action or result.
4. Rule Table
Modal Passive Structure
| Structure | Example |
|---|---|
| subject + modal + be + past participle | The report must be completed today. |
Examples with Different Modals
| Modal | Passive Example |
|---|---|
| must | The rules must be followed. |
| should | The report should be reviewed carefully. |
| may | The results may be published tomorrow. |
| might | The system might be improved in the future. |
| can | The problem can be solved easily. |
| could | The data could be analysed again. |
Negative Modal Passive
| Structure | Example |
|---|---|
| subject + modal + not + be + past participle | The equipment must not be used improperly. |
Example:
The rules should not be ignored.
5. Usage
1. Expressing obligation
Example:
Safety procedures must be followed at all times.
2. Giving recommendations
Example:
The data should be analysed carefully.
3. Expressing possibility
Example:
The results may be published next month.
4. Expressing capability
Example:
The problem can be solved using a different method.
5. Describing future possibilities
Example:
The system could be improved in future versions.
6. Signal Words
Modal passive constructions often appear with expressions indicating rules, recommendations, or possibility.
| Expression | Example |
|---|---|
| carefully | The report should be reviewed carefully. |
| immediately | The system must be repaired immediately. |
| possibly | The problem could possibly be solved. |
| soon | The results may be published soon. |
| properly | The equipment must be used properly. |
These expressions clarify how or when the action occurs.
7. Special Cases
Passive with Perfect Modals
Advanced structures combine modal verbs with perfect passive forms.
Structure:
modal + have + been + past participle
Example:
The system may have been damaged during the experiment.
Example:
The report should have been submitted earlier.
These forms refer to possible or expected past events.
Omitting the Agent
The agent is often omitted when it is unknown or unimportant.
Example:
The experiment must be completed today.
The sentence focuses on the requirement, not on who will complete it.
8. Additional Notes
Modal passive constructions are extremely common in:
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scientific writing
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technical instructions
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formal guidelines
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academic reports
Example:
The samples must be stored at low temperatures.
The focus is on the required procedure, not the person performing it.
9. Common Errors
⚠ Missing “be” in modal passive
Incorrect:
The report must completed today.
Correct:
The report must be completed today.
Explanation:
Modal passive requires be + past participle.
⚠ Incorrect verb form
Incorrect:
The data should be analyse carefully.
Correct:
The data should be analysed carefully.
Explanation:
The verb must be in the past participle form.
⚠ Incorrect negative structure
Incorrect:
The equipment must not used improperly.
Correct:
The equipment must not be used improperly.
Explanation:
The structure requires not be + past participle.
⚠ Incorrect perfect modal passive
Incorrect:
The system may have damaged during the test.
Correct:
The system may have been damaged during the test.
Explanation:
Perfect modal passive requires have been.
⚠ Incorrect verb agreement
Incorrect:
The samples must be analyses.
Correct:
The samples must be analysed.
Explanation:
Use the past participle, not the present form.
10. Lesson Mastery
After completing this lesson, you should now be able to:
✅ form passive constructions with modal verbs
✅ recognise how modal passives express obligation, possibility, and necessity
✅ understand structures such as must be done, should be completed, may be analysed
✅ avoid common errors in modal passive constructions