Please see the the attach photos. Our wedding photographer shot all of our pictures in shutter priority mode and ISO 6400. They are grainy, poor . Is there ANY way to fix them?
The photos can be improved, but you would have to pay a retoucher and even then with such a high iso the photos are going to look poor. Maybe pick out a few worth paying a retoucher from the actual day and do a reshoot with someone that knows what they are doing. I spent maybe four minutes in lightroom working on this. Adjusting contrast, black levels, white levels, and did some noise reduction but it is still very mushy in terms of sharpness.
Information that is not there is not there, there is no magic against that fact.
What you can do is de-noise them in professional software (for example Lightroom). They will certainly look better (the obvious color noise would be gone), but they will never get get crisp and sharp like an ISO 100 shot.
As others mentioned, there are other problems with the photo too - the sky is completely blown, etc. This is poorest amateur work.
Certainly in terms of the example you've provided, I would suggest looking at how you can recrop images to minimise the impact. In the example image, recrop the photo to a landscape, with the heads near the top, so that you can eliminate the sky. Unfortunately, there's not much that you can do about the overall lack of composition; at the end of the day, a woodland of bare deciduous trees is not the best backdrop.
As for the rest of the issues with it, as per Aganju's answer, quite rightly, professional software like Lightroom or Photoshop has tools that will be able to reduce the noise, adjust the tone and the contrast, perhaps also use Lightroom's Clarity and Vibrance sliders.
@MatthewWhited's comment is also spot on: a reshoot (using a professional photographer) is definitely the best solution. You should also review the contract you had with the photographer that you used (you did have a contract?) and see if you can get your money back.
I think this question serves as a great example to encourage people to research the wedding photographers and their portfolios and past work before booking them.
To me, this is a typical and not uncommon scenario:
My friend has a digital SLR, that friend is going to the wedding, it would make sense to ask them to do the wedding photos.
I've seen examples of this all too often...you only have to look through friends' facebook feeds to see it again and again.
I do agree with previous posters about the poor quality of that image, but you can fix things to some extent with software like Nik or Topaz Labs. A white sky can become (almost) beautifully blue with them and you can improve noise and other problems.
Proper photography software like Lightroom or Capture One would do too, but it wouldn't be as easy.
Example (done hastily):
It just seems as though sometimes the simplest answer is often overlooked. I don't know how experienced you are with photo editing, but I just did a couple of very, very basic things to alter the picture you used as an example. It wasn't a big process using Photoshop either. (Not sure why my entire answer nor the edited photo didn't appear here, but my edited photo is not the sample shown above.) I'll try again. (Hopefully, there will be a photo below this post... if so, that's the one.) lol
There are two plugins that really help when high ISO has been used: NeatImage and NoiseNinja.
I personally bought and use NeatImage professional to get rid of image noise. It does a fantastic job but it cannot fix a bad shot!
Shooting RAW is also helpful as you can change the exposure a few steps without destroying the image.
I'll take a shot at guessing what happened, it's highly possible the photographer used shutter priority set at 1/250th second or higher to reduce movement blur with an aperture of f16 or f22 for greater depth of field and overall sharpness and had Auto ISO turned on, but without EXIF data no one will ever know.
It's going to take a lot of work to even get acceptable results and could end up costing more than you expect, I did a few edits to the supplied JPEG and used cloning and NeatImage but the results are far from perfect. Sadly without the raw files you are not going to get anything close to good quality images.
Not exactly good but with a lot more work it could be better.
The 'Prime' denoising tool in DXO PureRaw is pretty much in a league of its own (although I hear Topaz's software is pretty good too). It's able to eliminate the noise without the type of blurring you often see with noise reduction algorithms.
I'm making one big assumption here though which is the photographer took the original photo using a RAW file. The properties dialogue you've posted indicates you have a jpeg. Is there a RAW original? If not, it's going to be very difficult to fix a jpeg in that condition.
(N.B. I'm in no way affiliated with DXO Labs.)