Pot and alcohol have had little effect on my metaphysical beliefs. Shrooms and e are a very different story. Both of these substances made me realize that I was completely missing the point of religion, and in fact, so are most people who fancy themselves pious.
I now see that religion is only a training exercise for the mind. The rites and rituals have no intrinsic value. There is no angel with a clipboard and a checklist, watching our every move in church and awarding points to those who run through the rigamarole most accurately. No, the truly wise church- or templegoer realizes that the real goal is the temperance, patience, quiet heart, feelings of awe, and tightly bonded communities that such disciplines foster. The chanting, recitation, sitting, standing, and processing are nothing but smoke screens. Once this realization is made, these virtues can be aimed for by ANY means, and the religious rites are not needed anymore. I remember thinking on shrooms one time that it's a shame so many religious people get lost in the hall of mirrors which is religious dogma. It's like buying a ticket, but then framing it on your wall instead of using it to gain admission to an awesome show.
I've also come to realize, while rolling, that God is a process and an event, rather than an entity. Like fire, in a way. I came to realize that God is an emergent property of human intelligence. God is nothing more than the vibes and actions generated whenever two or more sentient beings gather to be compassionate towards one another. Whoever said "God is Love" was pretty much spot on. In light of this, thought I, it's absolutely ludicrous to fight over/for God. God can't be fought for any more than a fire can be made with water.
So yes, in short, I've made some profound realizations about religion and spirituality while on drugs.