The short version: Metzee never asks you for a code, a password, a PIN, or a payment outside the app. A message asking for any of those is not from Metzee, however it looks.
The four, in detail
A one-time code. A code is for you to type into the app. Nobody — not support, not a seller, not anyone claiming to be either — ever needs you to read one out or forward it.
Your UPI PIN or bank password. Never, for any reason.
A payment outside Metzee. A transfer, a UPI handle, a wallet, a "direct deal to save fees". It removes every protection and it is against the rules. A seller suggesting it has told you how they handle problems.
A fee to release an order. No customs fee, no release fee, no verification charge. There is no such thing. Does it cost anything to buy on Metzee?
What a real message looks like
It arrives in the app, attached to an order or an enquiry.
It is specific about your order — the item, the number.
It does not create urgency. Pressure to act in the next ten minutes is the oldest tell there is.
Where fakes come from
A different channel. A message about your Metzee order arriving by SMS or on another app, from a number you do not know, is the commonest shape.
A link to a site that looks right. Check the address before you type anything into it. Fake Metzee websites and messages
A seller moving the conversation off the platform after a sale. Sometimes innocent, and still the thing not to do.
What to do
Do not reply. Replying tells them the number is live.
Do not tap the link.
Check in the app. If there is a real problem with your order, it is on the order.
Report it under Safety / report someone, with a screenshot. How to raise an issue
If you already gave something away
A code or a password: change what you can and tell Metzee immediately, under Account & login.
A payment: tell your bank first, then Metzee. Money sent directly is outside the system, which is exactly why it is the thing to refuse.
Nobody at Metzee will think less of you for it. This is a designed attack and it works on careful people. I lost the phone with my Metzee account
The habit worth having
Never act on a message. Act on the app. If a message says something needs doing, open the app and look. If it is real it is there; if it is not, you have lost nothing.
More: fake Metzee websites and messages, how to keep your account safe, what information does Metzee need.