Seen in pillar of fire, burning bush, Mt. Sinai, and in the flame on the alter. When Solomon's temple was dedicated in 2 Chr. Associated with divine wrath. Some of the events that are yet to occur, that are described in the Book of the Revelation will involve fire. It is associated with God's holiness, his jealousy, his protection, his righteous judgment, his wrath against sin, the Word of God, trial and suffering, of evil desire, of the tongue, and of heaven in its purity and glory.
Strange fire is no new thing today.
There are strange doctrines, strange practices, and strange thinking. That would mean something that God would not put his stamp of approval upon. There are a lot of doctrine, thinking, and practices in the local church that God would never put His Divine approval upon. It involves worship and service 2. It is a fleshly hype rather than God dependence.