Tom Bombadil is the eldest, older than
Treebeard, he came into existence when
Middle Earth was begotten, interesting he is somehow the opposite of
Morgoth's ring which is somehow an enchantment placed upon all Middle Earth. Ok, Tom Bombadil is..... the
MYSTERY ... of nature. He is a personification or rather the personification of the mystery of Middle Earth's nature and nature's mystery personified. He is nature's mystery and its mysterious magic which humans took a while to understand and allocate completely within the confines of science, which in fact science is the dry intellectual version of the understanding of the mystery of creation. Well, fable will not have much science unless its 'a mind of wheels and steel'
Saruman's mind or a light mention of his discovery of 'gun powder' or Morgoth's sciences which created the
dragons. Anyhow, this is fable and it would look quite strange if
Tolkien were to exchange fable's mysteries, diction and nomenclature with those we find in science fiction, such as Jules Verne etc etc etc. So who knows what
Gandalf would have wanted to know in his conversations with the mystery of nature and of creation?? it is a mystery too, Gandalf knew that Morgoth's ring ie the enchantment upon Middle Earth was also bound around Tom Bombadil, but then again
Sauron's ring had no effect on Tom Bombadil. Morgoth gone Tom Bombadil was probably freed from Morgoth and his ring, but this is another mystery... I personally think that Gandalf wanted to meet a friend, a firend whom he loved because Gandalf was the steward of all Middle Earth and cared for it and loved it and wanted to see it freed of Sauron, what best way to celebrate then to go and meet
Tom?? I think that it was love ...