This is actually a very fascinating question. It may help to consider the different types of bonding that you have learned about in class: ionic, covalent, and metallic. What is interesting is that in order to form a covalent bond multiple atoms normally share a given set of electrons to satisfy their electron requirement (think octet rule). Now what is unusual here is that noble gases fulfill their electron requirements themselves, they do not need to bond with other atoms to fill up their electron clouds (octets). Now, what appears to be happening in this study is that researches are using HUGE amounts of pressure to push both Xe and H very close to each other.When this happens the nuclei of the Xe and H atoms get very close to each other and some of the H atoms get close enough to the Xe atoms that they get inside their electron clouds. When this happens the electrons which are normally content being bound to the Xe atom can spill out and be shared with the H atoms which do not have a full electron cloud (remember H is not a noble has). In this way the Xe-H mixture becomes much more like a metal, where electrons act like a sea within the material and glue the material together. If you consider it in this manner, Xe is not really reacting with H, but rather just sharing some of its electrons while it is under pressure. I hope this helps answer your question, this is a very interesting concept.