Definition of opponent for English Language Learners. : a person, group, etc., that is against something (such as an action, law, or system) : someone or something that does not want something to exist, be done, etc.
Generally, your first mortgage payment is due on the 1st day of the 2nd month following your closing date. For example, if you close in February, your first mortgage payment will be due on Aproil 1st. Generally speaking of course.
Your first payment to your new lender, on May 1, will include all the interest charges from April 1 through the start of the new month. That's not unusual: Your lender will always include the interest from the previous month with every mortgage payment you make.