Bank loan to use as proof of funds for uk visa application

The reason why "funds parking" is a problem in the first place is that they don't want to give visas to people who can only afford to travel by borrowing money!

The reasoning is that since no responsible person would go into debt for a pleasure trip, something else must be up -- probably the applicant is considering the cost of travel to be an investment and hopes to find illegal work in the UK so he can send money home to pay off the loan. (Whether this reasoning is reasonable or not is a question that does not really belong here; the fact is that it is the reasoning visa authorities follow).

Since your claim is not merely that you're going on a random tourist trip, but attending a close relative's wedding, there ought to be a slightly larger chance that you can convince the ECO that it makes sense for you to travel for borrowed money. But even so you will still need to convince them that your economy is such that you can expect to be able to pay off the loan in a reasonable time after the trip.

For this you need bank statements, and an income with a reliable surplus to save or make loan payments from.

See our canonical explanation at Should I submit bank statements when applying for a UK Visa? What do they say about me?