Can i download my regular non-iTunes music on my iPhone?

So i have had an Android for the past 2 years, and I decided to switch to an Apple (I'm thinking of getting and iPhone 5s). Having had an Android, I never used iTunes. I usually just downloaded music onto my computer (which is a Windows PC), saved it onto a micro SD card, and put that in my phone. However, if i do get an Apple, would i have to download iTunes, and buy all that music I have? (it's quite a lot, and would come out to be very expensive for music I already own…) Or can I just download the music straight from my computer to the phone using the USB charger (or whatever other method)?

All of the MP3 files will transfer to the i platform. You will not have to repurchase the files you already have.

You will need to download iTunes on your PC (free on Apple.com) this will organize your files and make them available to your iPhone 5.

I started using iTunes Match and all of my files are available from iTunes if I purchased them from Apple or not. I'm not limited to the size of the memory on the phone to access my music library.