is melody alone enough for substantial similarity in music plagiarism?

hi the title is pretty explanatory. I'm finding this a bit hard to undrestsand. i heard that melody can be a big deciding factor if a song was plagiarized or not, but the issue is that if you don't take account rhythm and phrasing, then it would be unfair.

what i mean is, if two sheets of music have similar notes in consecutive, that does'nt necessarily mean they will sound similar, because the rhythm of it will make a piece same or different.

not sure if this is right place, but what y'all think>