No melodies will not sound weird alone. I usually start with a chord backing and build the song from there. Also a few things I've learned:
-Direction: Focus on going up, down or holding a small range of notes (usually around three) each measure with your melodies. Believe it or not, too much movement sounds unappealing, and there is nothing wrong with hitting the same note multiple times in a row. Moving upward actually creates a tensing effect, downward causes a more relaxing effect. If you can learn how to do your notes, you can create everything from dark brooding themes to soaring bright anthems. Just listen to the VIP of Golden Puppets and you can see a few of those strategies being used.
-Chord progressions: a lot of people can think the melody is what makes the song sound good, but if the melody is built on the wrong progression, it's not going to work as well. The best chord progression to start out with is the usual
I->V->vi->VI
or
i->VI->III->VII
but if you try to break out of those models, focus on making sure your chords work right. Lux was built on a IV->V->vi->iii progression, which is another great one to learn how to write melodies with.
-Chords and Melodies: it may seem like a cop-out, an un-original way of writing music, but if you can not only incorporate direction of your notes and making chords progressions work, but it's also a good idea to use notes from the chords to help make your melodies enhance your chords. Don't use only notes from those chords, switch it up and add some other notes, but make sure you're still using notes from your chords here and there.
-Syncopation, that'll help give your melodies a bit more presence in the song if they have a syncopation that makes them so they line up on different beats than the bass drum and snare in your percussion.
-Suspended and Resolving chords; those add more depth to chords that hold longer than most other chords. If you listen to the remix of Moar Growlz I did, the main drop progression is : Cm -> Ab9 -> Bbsus4 -> Bb -> Cm -> Eb -> Bbsus4 -> Bb
-Synthesizers: Believe me, the instrument makes the melody change quality and sound of the notes.
-Leitmotif's, look, one of my favorite things about music is making music that references other songs or portions of the same song. Have fun referencing your original works and even make them act as counter melodies to one another. If you'd want an example, go to 3:40 of What's Power and you can hear the chorus of Lux acting as a counter melody to the prime melody of the song.
https://soundcloud.com/davisjacobym/id- ... ox-version
Hope that helps!