So, what exactly was Kafka getting at in ‘The Metamorphosis’?
The human condition.
Alienation.
Impotence.
I think you should just read it as a beautifully written horror story, and let your mind reflect on what it reflects. That will be what it is about.
This link (and many others on the web) gives a more formal critique if you just want your homework doing.
Hve you guys noticed that if you read your usernames from bottob to top you get…
The Great Unwashed bum!
TGU, good link! I never really understood the more implicit meanings in it, and so have only enjoyed it as a “beautifully written horror story”. Likewise I’m now assuming there are deeper philosophical implications in The Castle , The Trial , and The Penal Colony all of which I’ve read and loved for the simple entertainment value (and I must admit in my ignorance that I found The Metamorphosis, which I read last, to be inferior to the other works).
I tried to use your link to get to philisophical analyses of the others, but when I clicked “back” at the bottom of the page it took me to a page with no links.
Anyway, I did a quick google search and mostly got essays for sale on the subject (apparently school essays on Kafka are a valuable commodity). Of course I seriously doubt I’d have any trouble finding 100’s of analyses of the other works, particularly The Castle, if I put in the effort (and had the patience to endure my crappy dial up internet connection) but if you happen to know of a similar link for The Castle offhand, it’d be swell if you could share. 
-Moe Zoid, The Great Unwashed Bum