Merging SFDC Account field with SFDC Lead field

Hello,

Is possible to merge an Account field with a Lead field from SFDC? If yes, which value will win?

We have a Company Revenue field and when it's a lead it shows the info that the person selected at the form, but once it's converted to a contact, it must show the account information - and not the one selected by the lead.

I appreciate any help.

Tks