Hi guys! I’ve been wanting to make a metal project for awhile, either doom or melodic power metal. The problem is I am not the best singer and I am new to song writing. My singing is more operatic?, mid to high range, so I thought doing a 1 album project not full-time band could be fun- however my songwriting skills and singing skills aren’t professional or amateur...

Any advice? More so for song-writing as I have had some advice for singing.

Find riffs that you find intriguing and make variations of them. For example you can do a variation on Scorpions Intro from In Search For The Peace Of Mind from G# A# C F and E F G#C to
G# C A# F and E G# F #C respectively in any key you want. Another idea is to be familiarised with the genre you want to play. You want to play power metal . Listen to a ton of it especially Helloween, Gamma Ray and try to get the layout of their riffs. Or you can sort of emulate their style of structuring songs. For example you have Rise And Fall By Helloween.
Start with only Drums then the vocals kick in, then there is a small pause and the vocals only play for too bars along with the harmonising voices etc etc. Another idea is to just record any riff it comes in your mind in one particular key and then connect them later. Eventually you'll get the hang of it. As for vocals I'd recommend some vocal power excercises by Aussie vocal coach. He is pretty good. There is also another one called strength and endurance increase with a thumbnail a body silhouette which is has some pretty challenging excercises.

Um, I don't know how to play any instruments except for a few notes on Guitar. I was hoping my project would be online-based. I forgot to mention that. Sorry.

Hmm then I'd suggest you search for a free midi-library with chord packs on YouTube, download it and experiment with whatever sounds good to your ear. Also for more preparation I'd suggest you learn a bit of theory regarding keys and intervals on whatever instrument you want but I'd recommend the piano. I recommend the piano because it"s pretty self-explanatory and you don't even need an expensive piano. Just get yourself a Midi-keyboard (with 25 keys it costs around 50 euros, mostly recommended for chords rhythm, then you have with 2 and 3 octaves whose prices depend on the manufactured. Also note that almost all 25 key midi keyboards have an octave changer).