Symbolism, Imagery, Allegory
You know what's interesting about all the movie and TV versions of this novella they make? They usually get Marley's ghost totally wrong.
Oh, sure, he's usually a totally creepy special effect, and the makeup tends to be ghoulish enough, and they even tend to recreate the jangling rattle noise that his chains make as he walks… but the chains themselves?
In every version Shmoop can remember, Marley's chains are shown to be just really big heavy metal chains, which is fine as it goes, we guess. Except that in the original, Marley actually looks pretty much the same as he did in life, but—and it's a huge but—he's bound and tied by something that is much more sinister and scary:
The same face: the very same. Marley in his pigtail, usual waistcoat, tights and boots; the tassels on the latter bristling, like his pigtail, and his coat-skirts, and the hair upon his head. The chain he drew was clasped about his middle. It was long, and wound about him like a tail; and it was made (for Scrooge observed it closely) of cash-boxes, keys, padlocks, ledgers, deeds, and heavy purses wrought in steel.
[…]
"You are fettered," said Scrooge, trembling. "Tell me why?"
"I wear the chain I forged in life," replied the Ghost. "I made it link by link, and yard by yard; I girded it on of my own free will, and of my own free will I wore it. Is its pattern strange to you?" (1.98-132)
What's the chain made out of? Not out of standard links at all, but instead out of the things that were most important to Marley before he died—money, debt, interest, profit. Why is this scarier, you ask? Well, maybe not scarier in a horror-movie kind of way, but certainly the idea that you will be manacled by the very things that you held up as important has a nice terror about it.
Think about it: this is specifically not a chain that's been made by some external force, some higher power that judges you after you die and that you can complain about not being fair or whatever. No, this is all your own doing—"I made it link by link of my own free will," says Marley in the above quotation, pointing out that the choice to what to value in life has endless ramifications, even beyond the grave.