In Microsoft Word, there are very many different kinds of fields. A field could be viewed as a dynamic text element, that is, the text displayed changes according to the rule defined by the user.
For this reason, fields cannot be treated as normal text, and they cannot be translated. However, in some case you have to adapt them. For example, when the source segment contains a field which displays a date, you might have to change the date format in the translation.
As fields cannot be translated anyway, you can simply copy them to have them included into the translation. In MetaTexis, you can use the Copy field function to do this. If the translation contains no field, this function copies the first field in the source segment. If the translation already contains one field, it copies the second field present in the source segment. If the translation contains two fields, it copies the third field in the source segment, and so on.