[ClaudiaM]

I bought by mistake metabisulphite instead of sodium sulphite, someone told me that they can be used interchangeably, is it true?

Sorry for any mistakes, I am not a chemist and english is no my native tongue.

[Borek]

Depends on the application, in general it is not impossible.

[ClaudiaM]

Depends on the application, in general it is not impossible.

Thank you for your help 
It is for protecting iron antique using process called alkaline sodium sulfite reduction

[Aldebaran]

Can you describe the procedure?

[Babcock_Hall]

Chemically dissolving metabisulfite in excess sodium hydroxide should produce solution identical with one made from sulfite, it is just a matter of a correct stoichiometry. Whether it will work as expected is another question, to be sure you should consult conservator-restorer. Such procedures tend to be highly sensitive to details.