I think the Portuguese Imperative is the_most_confusing verb tense to understand. I try and steer beginners far, far away from it because: Brazilians do not use this form with any consistency. What I really mean to say here is, they follow the rules of grammar, but they switch between the regular and the tu form without any real reason. But there is a method to the madness. Let me explain.
THE REGULAR VANILLA, CORRECT IMPERATIVE TENSE. It's not that hard.
> For AR verbs you just replace the a with an e.
> For ER & IR verbs you just replace the e with an a.
*HEY: we are just doing the ele/ela/você forms here! LET'S KEEP IT SIMPLE 😉
-ar regular verbs
|Tell me everything!||Me cont||e tudo!|
|Think again!||Pens||e bem!|
-er and -ir regular verbs
|Get out of here!||Sum||a daqui!|
|Open this door!||Abr||a essa porta!|
|Learn this!||Aprend||a isso!|
|Answer me!||Me respond||a!|
All in the world is right. You will hear all of these. These are correct and normal. But what about the irregular verbs? Irregular verbs take the same form as the present subjunctive (at least for the ele/ela/você forms). I told you this was confusing. It's advanced stuff because you really need to have a feel for the present subjunctive. I learned it by just getting used to hearing it in context. Only later did I learn the subjunctive. Look at some of the most common examples of the imperative of irregular verbs. Enter your best ZEN state and absorb these:
Some examples in the first person singular:
In reality, Brazilians use the tu form when conjugating the imperative. They do so for two reasons: When you're demanding something from someone you're often speaking in an extremely informal way with them. Look, check out that guy's sunglasses! - VERY INFORMAL. Eat your dinner! - VERY INFORMAL. The second reason is they will often choose the tu conjugation because it just sounds better(!). There are people that argue this point but there is really no better explanation. You can't say "Olhe só!" -- No one says that. "Olha só!" just sounds better.
Portuguese is normally an extremely consistent grammar to conjugate. The imperative is the big exception.
Some very common examples that use the TU form:
* Se liga = literally: connect yourself. Use it to say, wake up, open your eyes, don't be ignorant etc.
You will hear all of these almost every day. Get used to them. Se acostume!
Here is THE song for practicing the imperative. EVERY SINGLE PHRASE HAS THE IMPERATIVE! Seriously. Simply amazing. I've placed the version without concert video because it's subtitled for you to see the text.