One of the most common questions I'm asked is if fairies have physicality, if they are tangible beings. This is rooted I think in the common idea perpetuated especially in new age and post-Victorian fairy belief that these beings are entirely energy or thoughtforms, creatures that can be perceived by the mind but lack physical reality in this world. So let's dig into this shall we?
The simple answer is: yes, no, and maybe.
Because, really, nothing with fairies is simple.
The longer answer is that yes we have many accounts across mythology, folklore, and anecdotes that establish fairies are (or can be) physical in the human world but we also have stories were they are decidedly not. And that's the part we need to dig into.
In the oldest Irish myth featuring the Good Folk, the Echtra Condla, we see a woman of fairy appearing to Connla, son of the king of Ireland, and interacting with him in a physical way by giving him an apple and eventually taking him - physically - off in a boat. But she is also invisible and imperceivable to the other people around Connla. In the same way when we encounter a man of the sidhe in the Táin Bó Cuiligne he passes unseen and apparently intangibly through the army of Connacht but then is seen and interacts with Cu Chulain and his charioteer Laeg. Stories like that of Sadb and Fionn show the physicality of these beings as well, with Sadb - a woman of the sidhe - being rescued by Fionn and eventually giving him a son. In fact we have many stories across the entire corpus of material and across western European cultures of fairies of various kinds reproducing with humans.
There are also an array of stories that features predatory fairies that physically kill a human, such as the kelpie or each uisce who appear in the form of a horse, tempt a human to ride them, and then run off with the human and drown them before eating them. The Scottish Baobhan Sithe are beautiful women who tempt young hunters to dance with them only to kill them, and by all accounts they are physical beings. And of course selkies - well known across areas from Scotland to Iceland - are very physical beings who may be encountered as saviors of sailors in storms or may be trapped into unwilling marriages when their sealskins are stolen.
In contrast however we do find a few stories of fairy encounters where the beings seem intangible or able to do things beyond the normal limitations of our physical world. The Slua Sidhe flying unseen in whirlwinds may be one example. Will o the Wisps could be another, where lights are seen moving in trees, leading travellers astray, but appear and disappear without any connection to physical reality. There are also many anecdotal accounts of people experiencing fairies in non-physical ways which must be considered and of fairies seeming to vanish at will. This area is a bit muddier as some of this may be understood as invisibility rather than intangibility, but I'll still offer it for consideration here.
This may seem contradictory but its worth keeping in mind that the answer here doesn't have to be a simple yes or no. Reverend Robert Kirk writing about fairies in 1691 described their physicality as fluid and compared their nature to a condensed cloud, saying they could choose to be physical or choose to be intangible at their own will. Jacob Grimm relates a story of a German elf woman who passed through the knothole in a door as if she were smoke but once inside was fully physical, married and had children with the man who lived there, before leaving the same way she'd entered. He also described a method to capture Maran, or Mares, who were also known to enter through knotholes by blocking the knothole after they'd come in because while they could turn into something like smoke to pass through that small opening if it were blocked they would be trapped in their physical form. All of this seems to imply that physicality is a choice for the Good Folk, something that they can have or not have at will.
Are fairies physically real? Yes, according to the bulk of folklore, and no according to a few stories, and maybe both if we listen to Kirk and Grimm. Like everything else with this subject the answer is complex and ultimately nuanced.