While the lyrics of the song are heartbreaking on their own, I think in context it becomes something more than a ode to longing ala Phantom of the Opera.
It’s a song about dying and giving up.
Think about it: There are words like “never”, “always” and even the title itself, “evermore”, words which indicate a permanent state. The Beast doesn’t expect Belle to ever return. Part of it, of course, is that he believes that she doesn’t love him. We, as audience, know that it’s not true, that Belle already loves him, but simply hasn’t realized it herself. It would take her sense of freedom to be back, a violent mob and three bullets for her to come to grips with her feelings.
However, in his eyes, there is undeniable proof that she doesn’t return his feelings.
The spell isn’t broken yet.
Belle runs away and he’s still a Beast, all fur and claws and fangs and even more, his people are still cursed, objects.
He loves her and that’s why he set her free.
And then, Cogsworth spells out the harsh truth (that he and the rest of the stuff believes):
“Because she doesn’t love him.”
And that’s it.
The Beast believes that he failed to beat the clock and he’s doomed to be a Beast forever.
But, there’s more to it.
This remake turned the curse into something horrific. For the Prince (let’s just call him Adam ffs), it means remaining a Beast forever.
Forever, however, means something worse than just “all his life”. It does mean forever.
You see, it has been confirmed in an interview with Dan and Emma that
1. the Beast had been cursed for 9-15 years.
2. he didn’t age during that time.
The curse didn’t let Adam grow older: instead, it doomed him to be in this state forever. There is no aging and thus at some point, dying with this curse and, in a depressing and even cruel way, getting himself free from it. No, not even time can take it away.
So, when he sings “Forevermore”, he actually does mean forevermore. Unless someone kills him, or he decides to kill himself, he will go on being an immortal, ageless Beast locked in a “lonely tower” that crumbles and falls apart.
And it gets worse.
We saw that the changes they made to the curse in this version has the stuff turning into real objects, inanimate, without souls.
In other words… dead.
This curse will actually kill them.
And so, with this song, the Beast laments that he will be ageless, immortal, a pariah of the world… and alone.
“Lonely tower” literally means “alone” in this case. Not even his servants, the people who “looked after him all his life” will ever be able to even speak to him. He will be surrounded by objects which in reality would be their corpses.
That’s the curse in this remake.
And in this song, the Beast sings that he has accepted this fate. He let the only person who would ever help him escape this fate leave… because he loves her and he knows that since she doesn’t, it’s wrong to force her to stay.
One could ask: “Why doesn’t he kill himself, then? We saw it’s possible, with Gaston’s three bullets. He would at least be free from the curse, right?”
Morbid as it sounds, yes, this would be a way out for him. He’s ageless, but he can die of wounds.
Well, here comes the part in the song that states that no, the Beast will not resolve to this.
Belle is someone full of life, who wants “more than this provincial life”, who wants a “great adventure somewhere” who is full of hope. And this mindset of hers has affected him; he has gotten a bug for loving reading from her, for appreciating his life story and for connecting with another person.
She “inspire him, is a part of everything he does”. Belle’s memory will not let him end his cursed existence by his own hand.
He has lost even that morbid and depressing way out from the curse.
“Evermore” is a song that laments what is to come: an ageless existence completely alone, doomed to never, EVER end.
That’s why the Beast says “let them come” to Cogsworth when he tells him that there’s a mob coming. For him, it doesn’t matter. He’ll be a beast and unable to die anyway so, might as well, have these people relieve him from the curse sooner than later.
And he’s not even thoughtless about his servants: they’re doomed to fade away, to die anyway.
“Let them come” he says and he means it. “Let them kill all of us.”
In a sense, he’s even merciful. To himself more than to his servants, who held hope, but they at least have death to release them. He doesn’t even have that.
“Evermore” literally is an ode to one of the worst fates one can imagine.