The New Testament uses the word “to call” in more than one way. We can distinguish among three different ways in which we speak of divine calling.
There is the idea of “a calling” we have that is a vocation, where God calls us to a particular task, or a particular ministry, or a particular career. We call that a _vocation_, which is simply the word for “to call.”
We also talk about the distinction between the outward call, or the external call of God, and the internal call of God. The outward, external call is that which is proclaimed indiscriminately to everyone who hears the preaching of the gospel. When we proclaim Christ to the world, anybody who is within earshot can hear the outward or external call to come to repentance and to come to Christ.
I don’t think Paul is talking about the external call in Romans 8:30 when he talks about “calling” in the golden chain. In the context, all of those who are called are justified, so that can’t possibly refer to the external call because not everybody who hears the external call comes to faith, justification, and glorification.
In addition to the outward call, there is the inward call. In theological terms, this is known as “effectual calling.” It is the internal call by which God calls His elect to Himself through the power of the Holy Spirit, changing the disposition of their hearts through regeneration. The inward call that is accomplished by the Holy Ghost is effectual in that it brings about God’s desired and decreed consequence.
The inward call is irresistible, not in the sense that I don’t have the power to resist it, but my resistance cannot overcome it. God’s effectual call effects what He intends it to do; namely, to bring us to saving faith.