Clitic Pronouns
Eu o amo!
In English, some words like I or he change after a verb, like in she loves me. Something similar happens in Portuguese, but words like me go before the verb!
Ele me ama.
He loves me.
Eu te amo.
I love you.
Eu o amo.
I love him.
Eu a amo.
I love her.
Ele nos ama.
He loves us.
Eu os amo.
I love them.
Eu as amo.
I love them.
If you are talking about someone receiving something, like in I give money to him, use lhe and lhes.
Eu lhe dou dinheiro.
I give money to her / him.
Eu lhes dou dinheiro.
I give money to them.
But the words me, nos and te never change!
Ela te ama.
She loves you.
Ela te dá dinheiro.
She gives money to you.
Eu amo elas!
Even though eu os amo is one way to express love in Portuguese, in Brazil it's very common to hear eu amo eles. That is also true for o, a, and as, which are replaced by ele, ela, and elas.
Ela a ama.
She loves her.
Ela ama ela.
She loves her.
Don't forget to love yourself!
When someone is doing something to themselves, use se.
Ela se ama.
She loves herself.
But sometimes that might not be clear for you! Some special verbs require an extra se that doesn't have an equivalent translation in English.
Ele não se esquece do leite.
He (himself) does not forget the milk.
Ela se parece com a mãe.
She (herself) looks like her mother.