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 can be used together with passive constructions to express meanings such as:
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obligation
-
necessity
-
possibility
-
permission
Example:
The experiment must be repeated.
Here the modal must expresses obligation, while be repeated forms the passive structure.
Modal passive constructions are common in academic writing, scientific reports, and formal instructions, where the focus is placed on actions or procedures rather than the person performing them.
By the end of this lesson, you will be able to:
-
explain how modal verbs combine with passive voice
-
construct sentences using modal + be + past participle
-
use modal passive forms to express obligation, possibility, and necessity
-
identify and correct errors in modal passive constructions
2. Concept Introduction
Consider the following active sentence:
Researchers must repeat the experiment.
Passive form:
The experiment must be repeated.
Notice how the object of the active sentence becomes the subject of the passive sentence.
| Active Sentence | Passive Sentence |
|---|---|
| Researchers must repeat the experiment. | The experiment must be repeated. |
The modal verb must remains unchanged, while the passive structure be + past participle is added.
3. Core Explanation
Modal passive constructions follow a simple grammatical pattern:
subject + modal verb + be + past participle
Example:
The report should be reviewed carefully.
Here:
| Element | Function |
|---|---|
| report | subject |
| should | modal verb |
| be reviewed | passive verb phrase |
This structure allows modal verbs to express different meanings within passive sentences.
Obligation
Modal verbs such as must and should can express obligation in passive constructions.
Example:
The equipment must be inspected regularly.
Possibility
Modal verbs such as may, might, and could express possibility.
Example:
The results may be published next week.
Ability or Permission
Modal verbs such as can may also appear in passive constructions.
Example:
The device can be repaired easily.
4. Rule Table
Basic Modal Passive Structure
| Structure | Example |
|---|---|
| subject + modal + be + past participle | The experiment must be repeated. |
Modal Passive Examples
| Modal | Meaning | Example |
|---|---|---|
| must | obligation | The procedure must be followed carefully. |
| should | recommendation | The data should be analysed again. |
| may | possibility | The results may be published tomorrow. |
| might | weaker possibility | The experiment might be repeated later. |
| can | ability / possibility | The system can be repaired easily. |
5. Usage
1. Expressing obligation
Example:
The safety guidelines must be followed carefully.
2. Expressing recommendation
Example:
The data should be analysed again.
3. Expressing possibility
Example:
The results may be published soon.
4. Expressing potential outcomes
Example:
The system could be improved with new software.
5. Expressing capability
Example:
The equipment can be repaired quickly.
6. Signal Words
Certain expressions commonly appear with modal passive constructions.
| Expression | Example |
|---|---|
| must | The instructions must be followed carefully. |
| should | The data should be reviewed again. |
| may | The results may be announced tomorrow. |
| might | The procedure might be modified later. |
| can | The device can be repaired easily. |
These words indicate the speaker’s judgement or level of certainty.
7. Special Cases
Modal Perfect Passive
This structure expresses possibility or deduction about past events.
Structure:
modal + have + been + past participle
Example:
The report may have been completed earlier.
Example:
The results must have been analysed incorrectly.
Passive in Scientific Instructions
Modal passive constructions are frequently used in procedural instructions.
Example:
The samples must be stored at low temperatures.
This structure emphasises the procedure rather than the person performing it.
8. Additional Notes
When converting active modal sentences to passive voice:
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The object becomes the subject.
-
The modal verb remains unchanged.
-
The structure be + past participle is added.
Example:
Active:
Researchers must analyse the data.
Passive:
The data must be analysed.
9. Common Errors
⚠ Missing “be” in modal passive
Incorrect:
The experiment must repeated.
Correct:
The experiment must be repeated.
Explanation:
Modal passive requires modal + be + past participle.
⚠ Incorrect past participle
Incorrect:
The report should be wrote today.
Correct:
The report should be written today.
Explanation:
Passive voice requires the past participle form.
⚠ Using modal with active structure incorrectly
Incorrect:
The results must analysed carefully.
Correct:
The results must be analysed carefully.
Explanation:
Passive structure requires be + past participle.
⚠ Incorrect word order
Incorrect:
The experiment be must repeated.
Correct:
The experiment must be repeated.
Explanation:
Correct order: modal + be + past participle.
⚠ Incorrect modal perfect passive
Incorrect:
The results may have analysed earlier.
Correct:
The results may have been analysed earlier.
Explanation:
Past passive probability requires have been + past participle.
10. Lesson Mastery
After completing this lesson, you should now be able to:
✅ explain how modal verbs combine with passive voice
✅ construct sentences using modal + be + past participle
✅ use modal passive forms to express obligation, possibility, and necessity
✅ identify and correct errors in modal passive constructions