RULES OF MODAL VERBS
| Rule | Example |
|---|---|
| 1. Modals never change form. | We CAN swim. Not cans. |
| 2. Modals are followed by the base verb. | She WILL GO. |
| 3. Modals do not take "to" before the verb. | He MUST LEAVE. Not must to leave. |
| 4. Use CAN for ability. | She CAN SING well. |
| 5. Use COULD for past ability. | H COULD RUN fast when young, |
| 6. Use CAN for permission (Informal) | You CAN BORROW my pen. |
| 7. Use MAY for formal permission. | You MAY ENTER now. |
| 8. Use MUST for strong obligation. | You MUST WEAR a seatbelt. |
| 9. Use HAVE TO for necessity. | I HAVE TO FINISH homework. |
| 10. Use MUST NOT (MUSN'T) for prohibition | You MUSTN'T SMOKE here. |
| 11. Use SHOULD for advice. | You SHOULD EAT healthy food. |
| 12. Use OUGHT TO for moral duty. | We OUGHT TO RESPECT our elders. |
| 13. Use SHALL for suggestions (formal). | SHALL WE GO for a walk? |
| 14. Use SHALL for offers (formal). | SHALL I OPEN the window? |
| 15. Use WILL for future certainty. | She WILL TRAVEL tonporrow. |
| 16. Use WOULD for polite requests. | WOULD YOU HELP me? |
| 17. Use WOULD for past habits. | When young, he WOULD PLAY outside. |
| 18. Use COULD for polite requests. | COULD YOU PASS the salt? |
| 19. Use MIGHT for weak possibility. | It MIGHT RAIN later. |
| 20. Use MAY for strong possibility. | It MAY SNOW tonight. |
| 21. Use MUST for logical deduction. | She's absent. She MUST BE sick. |
| 22. Use CAN'T for logical impossibility. | He CAN'T BE 100 years old! |
| 23. Use SHOULD for expectations. | The train SHOULD ARRIVE soon. |
| 24. Use WOULD for unreal situations. | I WOULD TRAVEL if I had money. |
| 25. Use COULD HAVE fo past possibility. | He W0ULD HAVE WON, but he fell |
| 26. Use SHOULD HAVE for past advice not taken. | You SHOULD HAVE STUDIED harder. |
| 27. Use MUST HAVE for past deduction. | He MUST HAVE FORGOTTEN the key |
| 28. Use CAN'T HAVE for past impossibility. | She CAN'T HAVE SEEN me. |
| 29. Use MIGHT HAVE for past possibility. | He MIGHT HAVE MISSED the bus. |
| 30. Use WOULD HAVE for unreal past. | I WOULD HAVE HELPED if I'd known. |
| 31. Modals don't take -s in third person. | She CAN SWIM. Not cans. |
| 32. Modals don't use infinitives after them. | We MUST GO. Not must to go. |
| 33. Modals don't use participles after them. | He SHOULD TRY. Not should tried. |
| 34. Use CAN for general truths. | Oil CAN FLOAT on water. |
| 35. Use MAY in academi language. | Results MAY SUGGEST new theories. |
| 36. Use MUST for strong personal opinions. | This movie MUST BE the best! |
| 37. Use SHOULD for probability. | Prices SHOULD DROP soon. |
| 38. Use SHALL in legal documents. | Tenants SHALL PAY rent on time. |
| 39. Use WILL for instant decisions. | I'm thirsty. I WILL GET water. |
| 40. Use WILL for promises. | I WILL ALWAYS LOVE you. |
| 41. Use WILL for predictions. | It WILL RAIN tomorrow. |
| 42. Use WOULD in reported speech. | She said she WOULD CALL me. |
| 43. Use COULD for tentative possibility. | We COULD TRY later. |
| 44. Use CAN with senses. | I CAN HEAR music. |
| 45. Use CAN'T for strong refusal. | I C N'T ALLOW that. |
| 46. Use MIGHT for uncertain suggestions. | We MIGHT GO shopping. |
| 47. Use SHOULD for polite suggestions. | You SHOULD REST a little. |
| 48. Use MAY for blessings. | MAY YOU LIVE long! |
| 49. Use CAN for informal offers. | I CAN HELP you. |
| 50. Use WOULD in conditionals (Type 2). | If I were you, I WOULD STUDY |
| 51. Use WOULD HAVE in conditionals (Type 3). | If I had seen him, I WOULD HAVE SPOKEN. |
| 52. Negative of MUST = lack of necessity (BrE). | You NEEDN'T COME early. |
| 53. Negative of MUST = prohibition (AmE). | You MUST NOT ENTER. |
| 54. NEED NOT = not necessary. | You NEED NOT WORRY. |
| 55. DARE NOT = lack or courage. | .I DARE NOT SPEAK to him |
| 56. OUGHT TO for near certainty. | HePUGHT TO ARRIVE by now. |
| 57. Use SHOULD in conditionals. | If you SHOULD SEE him, tell me. |
| 58. SHALL in first person = determination. | I SHALL SUCCEED. |
| 59. WILL in first person = willingness. | I WILL HELP you. |
| 60. SHALL in second/third person = command. | You SHALL NOT PASS. |
| 61. MAY in academic writing = cautious claims. | The study MAY INDICATE bias. |
| 62. MIGHT as more tentative than MAY. | It MIGHT NOT WORK. |
| 63. CAN with verbs of perception. | I CAN SEE stars. |
| 64. WILL in habitual actions (literary). | He WILL SIT by the fire every night. |
| 65. WOULD in habitual past. | He WOULD ALWAYS SMILE at strangers. |
| 66. MUST for urgency. | You MUST ACT now. |
| 67. SHOULD for duty. | We SHOULD HELP the poor. |
| 68. SHALL for inevitability. | Justice SHALL PREVAIL. |
| 69. COULDN'T for inability. | I COULDN'T SOLVE the puzzle. |
| 70. MAY NOT * CANNOT. | You MAY NOT PARK here (not allowed). |
| 71. MIGHT AS WELL for weak suggestion. | We MIGHT AS WELL LEAVE now. |
| 72. HAD BETTER stronger than should. | You HAD BETTER STUDY. |
| 73. CAN in requests (informal). | CAN YOU HELP me? |
| 74. COULD in polite requests. | COULD YOU TELL me the time? |
| 75. WOULD YOU MIND ing. | WOULD YOU MIND OPENING the door |
| 76. SHOULDN'T HAVE = past mistake. | You SHOULDN'T HAVE LIED. |
| 77. NEEDN'T HAVE = unnecessary past action. | We NEEDN'T HAVE HURRIED. |
| 78. CAN'T HELP + -ing. | I CAN'T HELP LAUGHING. |
| 79. MIGHT NOT HAVE = past uncertainty. | He MIGHT NOT HAVE KNOWN. |
| 80. MUSTN'T = prohibition. | You MUSTN'T TOUCH that. |
| 81. SHAN'T = refusal (BrE). | I SHAN'T GO. |
| 82. WILL NOT (WON'T) = refusal. | He WON'T LISTEN. |
| 83. SHALL with "l/we" in questions = offers. | SHALL WE DANCE? |
| 84. WOULD RATHER + base verb. | I WOULD RATHER STAY home. |
| 85. WOULD SOONER = preference. | I WOULD SOONER DIE. |
| 86. CAN'T POSSIBLY for strong refusal. | I CAN'T POSSIBLY AGREE. |
| 87. MUST SURELY = strong assumption. | She MUST SURELY KNOW this. |
| 88. WILL PROBABLY for likelihood. | He WILL PROBABLY COME. |
| 89. SHOULDN'T REALLY = soft advice. | You SHOULDN'T REALLY SAY that. |
| 90. MIGHT WELL = strong likelihood. | This MIGHT WELL BE true. |
| 91. CAN ALWAYS = reassurance. | You CAN ALWAYS ASK me. |
| 92. COULD ALWAYS = weak suggestion. | You COULD ALWAYS CALL him. |
| 93. MAY AS WELL = logical option. | We MAY AS WELL WAIT. |
| 94. SHALL NEVER = strong refusal. | I SHALL NEVER FORGIVE you. |
| 95. WILL NEVER = strong refusal. | I WILL NEVER AGREE. |
| 96. MIGHT NEVER = possibility of not. | Sh MIGHT NEVER RETURN. |
| 97. CAN HARDLY = almost not. | I CAN HARDLY BELIEVE it. |
| 98. COULD HARDLY = past difficulty. | We COULD HARDLY HEAR him. |
| 99. MIGHT JUST = small chance. | He MIGHT JUST WIN. |
| 100. WILL CERTAINLY = definite. | She WILL CERTAINLY PASS. |
| 101. WOULD CERTAINLY = definite in imagined past. | I WOULD CERTAINLY HAVE HELPED. |