The poetic meter of ljóðaháttur:

Two units of three lines each.

The first two lines in each unit are tied together by alliteration, and the third is also decorated with alliteration.

Lines 1, 2, 4, 5: two accented syllables per line.

Lines 3, 6: two or three accented syllables per line (sometimes four).

A stressed syllable beginning with a vowel is considered alliterative with any other vowel.

Optional: rhyme, half-rhyme, partial-rhyme

Example:

1. Wisdom, mettle,
2. might and wit
3. suit a prince's son;

4. open-handed,
5. warm of heart
6. till his days are done.

(Accented syllables: in bold)

Lines 1 and 2 are doubly tied together with alliteration: wisdom+wit, mettle+might

Lines 4 and 5 are tied together with alliteration: handed+heart

Line 3 contains two alliterations: suit+son

So does line 6: days+done

Half-rhyme: might+wit

Rhyme: son+done

Definitions:

alliteration:
-- two or more words beginning with the same or similar consonant, as in "bed and breakfast"
-- two or more words beginning with any stressed vowel, as in "each and all"...where "each" and "all" are stressed but "and" is not

rhyme:
-- words whose last vowels sound the same, along with any consonants following those ending vowels, as in "who, true" or "hat, cat" or "mention, intention"

half-rhyme:
-- words whose ending consonants sound the same (though not the last vowels) as in "big, leg, tug"

partial rhyme:
-- words whose last accented vowels sound the same (though not the final consonants) as in "last man standing"