I was just trying to have an investigate of some of the S2 images on SNAP and for most of them I can open them with the MTD_MSIL1C.xml file but for some of the images that file does not exist. Is there another way to open them in SNAP if the MTD_MSIL1C.xml file is missing?
No, there is no reasonable way opening the files if this file is missing. This must be present. Probably your S2 images are corrupted.
You can open the jp2 files separately, but this doesn’t make much sense.
Hello @emma
If you have Tiles with missing metadata, then an email to eosupport@copernicus.esa.int might help clarify the situation - and if an issue is confirmed, it will no doubt trigger our investigation into your issue 
Cheers
Jan
Jan Jackson
S2 MPC Operations Manager