The stuffy way of talking about form and meter in "The Tyger" is to say it's written in six quatrains of rhyming couplets with a pulsing, steady, mostly-trochaic rhythm. OK, now is the time to ask, "What the heck does that mean?"
Let's start from the beginning. A quatrain is a stanza with four lines. Rhyming couplets are pairs of lines, the last words of which rhyme. We know what you're thinking: in the first and last stanzas, "eye" doesn't rhyme with "symmetry." However, they do rhyme if you pronounce "symmetry" in an old-fashioned way, as "simm-a-try" (as in "I’m gonna try"). So two lines make a couplet, and two couplets make a quatrain or stanza. Lastly, six stanzas make a poem – it’s neat, clean, and simple.
The "trochaic" refers to the "trochee," of one stressed syllable followed by one unstressed one (DUM-da, DUM-da, etc.). "The Tyger" isn't all trochaic, because there are several exceptions, but the general rhythmic march when you read it out loud is quintessentially trochaic.
"The Tyger" is an example of a clear and definable form. Good luck finding anything similar in Blake’s other work beyond the Songs, it’s really just not his style. He generally prefers long, prose-like lines with seemingly random punctuation. To illustrate what we mean, check out this particularly dramatic section from Blake’s poem America:
As human blood shooting its veins all round the orbed heaven
Red rose the clouds from the Atlantic in vast wheels of blood
And in the red clouds rose a Wonder o’er the Atlantic sea;
Intense! Naked! A Human fire fierce glowing, as the wedge of iron heated in the furnace; his terrible limbs were fire
With myriads of cloudy terrors banners dark & towers
Surrounded; heat but not light went thro’ the murky atmosphere
…And so on. So, incredible imagery, almost bonkers visions, stuff that makes you say "what the heck?" yet urges you to read more. But there's definitely no rhyme, no meter, no clear stanzas, no repetition, not even proper punctuation. This is Blake at his other extreme.