I'm familiar with にている and みたい however I'm looking for a way to say something is something without literal implications. For example Michael Phelps is a fish. Like he's not literally a fish so i wouldn't want to say Michael Phelps は 魚 だ。
Any help on this subject would be great thanks.
So you want to make a metaphor in its narrowest sense, something that does not use any explicit word like like, as, resemble, compare, (の)ような, みたいな, 似ている?
Then the solution is simple; use XはYだ/です, and let the listener notice the metaphor. It appears structurally identical to an ordinary sentence, but that's the definition of metaphor (in the narrow sense), after all.
- 君は太陽だ。
You are my sun.- お父さんは悪魔だ。
My father is a demon. (= a cruel person)- 男はみんなオオカミだ。
(literally) All men are wolves. (= sexually aggressive person, woman chaser)- 彼は天狗になっている。
He has become a tengu. (= big-headed person)
Please keep in mind that each culture has its own set of known metaphors. A metaphor that works in your culture may not work in different cultures. I believe "you are my sunshine" and "you are a demon" work almost in the same way in English and in Japanese. But "you are a wolf" has different implications, and "you are a tengu" obviously does not make sense in English. Conversely, "you are a chicken" makes perfect sense in English, but 君はニワトリだ makes almost no sense in Japanese.
Regarding fish, ～は魚だ ("～ is a fish") is not a well-known metaphor at least in the Japanese culture. People can instantly understand you are trying to make some metaphor, but they cannot get the implication. Still, in creative writings like poems, you can always say 君は魚だ instead of 君は魚みたいだ/君は魚に似ている, and explain it later.
I think your premise is flawed. A metaphor, by definition, directly equates two things for the sake of comparison or symbolism with the implication that they are not literally the same thing. So you would say
Michael Phelps は魚だ。
But what I think you might be looking for is ～に[例]{たと}える／[譬]{たと}える.
Michael Phelps をよく魚にたとえる。 → (People) Often compare Michael Phelps to a fish.
Keep in mind that this always carries "compare(s) to" in the translation, which then makes it no longer a metaphor. See also 隠喩(いんゆ)とは.
I found this nice guide on metaphors: http://kokugoryokuup.com/hiyu-meaning/
So "のように", "のようだ", etc. are one way to do metaphors:
「山田くんは太陽のように明るい子だ。」
Yamada-kun is a child that is bright like the sun.
... but it's also possible to equate things directly:
「人生はドラマだ。」
Life is a drama.
So comparing things directly or using のように are both possible, but you have to consider whether the person reading what you wrote will understand what you meant.
I invite you to look at the examples and explanations on the web page linked above.
By the way, note that "によると" means "according to". It's not really used for comparison.
