riddle - The Answer Would Make a Good Title

Here is a riddle quite long
I hope you can follow along
You'll be delighted
While I recite it:

I'm known to be unmatched in song.

You'll find me the whole world around
In nature 'tis true I abound
You might not expect
But just recollect:
In various forms I am found.

I am a king of my kind
And yet I have been quite maligned
Confused for another
Get this: I'm her brother

Though our differences are well defined.

We're nothing alike, I insist
Her flowery form I resist
I'm more aggressive
She seems more passive
Yet one step from outburst she is.

She's one of a number, all true
I'm not because I come from two
She gets her own line
I'll never have mine

You know me now surely, don't you?

See me or listen to flyers
Read me or climb up much higher
Once solving is done
Please pardon the pun
And now I must sleep, for I tire.

I worked pretty hard on this one; I wanted it to be challenging but doable. Don't take things too literally on this one and you won't be misled. As always, the green check goes to not only the correct final answer, but the one that also explains all of my hidden clues. I hope you guys enjoy!

ADDED STANZA This should be the nail in the coffin; then the hard work will be in finding all of the hidden--and cute, if I do say so myself--clues in the limerick. But beware, like in the rest of the limerick, don't take everything literally here. Wordplay abounds in this stanza. :

From all but one sense do we hide
My ghostly sister and I
She on a petal
Me on a metal
I've made many emperors die.

Answer

You are

Purple, or possibly "The color purple", which might make a good title.

Here is a riddle quite long
I hope you can follow along
You'll be delighted
While I recite it:
I'm known to be unmatched in song

Unmatched in song: there is no rhyme for purple, although this hasn't stopped people trying (then I'll hurtle like Steve Urkel on a turtle in a circle, the feeling's universal like the hurtful color purple) :

You'll find me the whole world around

In nature 'tis true I abound
You might not expect
But just recollect:
In various forms I am found.

There are lots of purple plants and birds, e.g. aubergine (eggplant), lavendar, heather, grapes, purple heron, purple finch.

I am a king of my kind
And yet I have been quite maligned
Confused for another

Get this: I'm her brother
Though our differences are well defined.

Purple is a regal colour. But purple looks quite a bit like violet, which is a female name, so we can call purple her brother

We're nothing alike, I insist
Her flowery form I resist
I'm more aggressive
She seems more passive
Yet one step from outburst she is.

Violet is a flower. And a viole(n)t act is an outburst. As @Mythi commented, You can be purple with rage, or a shrinking violet.

She's one of a number, all true
I'm not because I come from two
She gets her own line
I'll never have mine
You know me now surely, don't you?

Violet is a color with a single wavelength (a spectral colour). But purple is a mix of Red and Blue, with two distinct wavelengths (a non-spectral color). This means (see comment from @Jon Ericson) that violet is counted as one of the lines of the rainbow, but purple isn't, with one musical exception

See me or listen to flyers
Read me or climb up much higher
Once solving is done
Please pardon the pun
And now I must sleep, for I tire.

You can see purple, and could read the book The color purple, or alternatively purple prose (comment from @Mythi). The Stone Temple Pilots released an album called Purple, and in this case are the Flyers (comment from @Jon Ericson). The pun is on "tire/Tyre". The ancient city of Tyre was source of a purple dye, known as Tyrian purple: "As early as the 15th century BC the citizens of Sidon and Tyre, two cities on the coast of Ancient Phoenicia, (present day Lebanon), were producing purple dye from a sea snail called the spiny dye-murex "

From all but one sense do we hide

My ghostly sister and I
She on a petal
Me on a metal
I've made many emperors die.

Violet and purple can only be seen, not smelt/touched/tasted/heard. And being an E-M wave is quite ghostly. Petal is again a reference to the flower violet. Metal could refer to Manganese based pigments which can be purple, but the intended meaning was the Purple Heart Medal, awarded to injured US military personnel. Some emperors (e.g. Charlemagne) were buried in purple robes. And there may very well be a pun on die/dye.