Meaning
To stick one's nose in / To butt in
Example
Ninguém pediu sua opinião, pare de meter a colher na vida dos outros!
Nobody asked for your opinion, stop sticking your nose in other people's business!
Origin
The image behind meter a colher ("to stick the spoon in") comes from the kitchen and the shared table: dipping your spoon into a pot or dish that someone else is tending. Doing so means interfering where you were not invited, which is exactly the figurative sense — butting into other people's business.
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More idioms
Acertar na moscaTo guess correctly / To hit the nail on the headAmigo da onçaA fake/false friendAndar na linhaTo toe the line / To behave properlyArmar um barracoTo cause a public sceneRodar a baianaTo cause a public scene / To go ballisticArrumar sarna pra se coçarTo ask for troubleArrastar as asasTo hit on someone / To flirtAbrir o jogoTo come clean / To open upArregaçar as mangasTo roll up one's sleeves / To get to workAgarrar com unhas e dentesTo hold on for dear life / To seize an opportunity