Formal:
* Olá, meu nome é... (Formal, used with strangers or someone you don't know well)
Informal:
* Oi, meu nome é... (Informal, used with friends and family)
* E aí, meu nome é... (Very informal, used with close friends)
You can also use:
* Prazer em te conhecer, meu nome é... (Nice to meet you, my name is...) - This is a polite way to introduce yourself, both formal and informal.
It's important to note that Brazilian Portuguese has a lot of regional variations. The way you say "hello" might differ slightly depending on the region.