Indeed you can, that's the kind of thing they're commonly used for. A mailmerge would use, say, an Excel file with different columns (fields) for each of:
• Name
• Address
• Locality
• State
• Zip/Post Code
• Past Due
• Payment(s) Received
• Latest Charges
• Taxes
• Total
Some of these might require more than one column (e.g. you might have Name, Company Position, Company name, etc) or might be split (e.g. Street # & Street Name instead of the lot in one Address field) or, if you're not concerned with granularity, you might combine Locality, State & Zip/Post Code in a single column (field). The Total could be calculated from the others.
For an idea of what can be achieved, see:
https://www.msofficeforums.com/mail-...html#post23345
https://www.msofficeforums.com/mail-...html#post30327
Most mailmerges don't require that level of complexity, though.