According to John Ronald Reuel Tolkien’s own words, as mentioned in his Letter #211, dating from 1958, this is what the eminent author had to say about the ‘One Ring’ and its association with power –

The Ring of Sauron is only one of the various mythical treatments of placing one’s life, or power, in some external object, which is thus exposed to capture or destruction with disastrous results to oneself. If I were to ’philosophize’ this myth, or at least the Ring of Sauron, I should say it was a mythical way of representing the truth that potency (or perhaps rather potentiality) if it is to be exercised, and produce results, has to be externalized and so as it were, passes to greater or less degree, out of one’s direct control.

From the lore perspective, this externalized power of Sauron translates to the ultimate desire to rule over all. And this tantalizing scope is epitomized by the famous ‘One Ring’ poem of The Lord of the Rings – part of which is inscribed on the ring itself. And we daresay, the ambit becomes even more enthralling when the short poem is uttered by none other than J.R.R. Tolkien himself

Three Rings for the Elven-kings under the sky,
Seven for the Dwarf-lords in their halls of stone,
Nine for Mortal Men doomed to die,
One for the Dark Lord on his dark throne
In the Land of Mordor where the Shadows lie.
One Ring to rule them all, One Ring to find them,
One Ring to bring them all and in the darkness bind them
In the Land of Mordor where the Shadows lie.

Interestingly enough, the words of the inscription on the ‘One Ring’ are in the Black Speech. the very language devised by Sauron to be spoken in the realm of Mordor – according to Tolkien’s veritable legendarium. However, in spite of the language itself, the script used for the inscription pertains to Elvish letters, specifically entailing the Tengwar – which was said to be created by Fëanor, the original lord of the Silmarils. To that end, Gandalf fiercely speaks the famous phrase from the ‘One Ring’ poem in Black Speech, during the episode of the Council of Elrond, in a bid to temper the bickering of his allies –

Ash nazg durbatulûk, ash nazg gimbatul,
Ash nazg thrakatulûk agh burzum-ishi krimpatul.

Translated in ‘Common Speech‘:

One ring to rule them all, one ring to find them,
One ring to bring them all and in the darkness bind them.

And finally, in case one craves for a more dramatic exposition, you can also hear the ‘One Ring’ poem being read by the late and great Christopher Lee. He goes on to cover the Ring-inscription lines in Mordor’s Black Speech –