The basic pattern of iambic trimeter is: * / | * / | * /

These are examples of iambic trimeter, though with many substituted feet. This first is by Robert Herrick. The line "Things to perfection" should be read, "Things to per-feck-shee-on." This is an example of diaeresis--and also of substitution, in that the first stress falls on "Things," making the scansion: / * | * / | * /.

                            By all aspects that bless
                            The sober sorceress,
                            While juice she strains, and pith
                            To make her philtres with;
                            By Time, that hastens on
                            Things to perfection;
                            And by your self, the best
                            Conjurement of the rest;
                            --O, my Electra!  be
                            In love with none but me.
 

Christina Rossetti leads off each the stanzas of "Dream Land" with iambic trimeters:

                                Where sunless rivers weep
                                 Their waves into the deep,
                                She sleeps a charmed sleep:

And here is a stanza from John Keats's "Stanzas" (the feminine rhymes result in some hypermetric syllables):

                    Ah! would 'twere so with many
                       A gentle girl and boy!
                    But were there ever any
                      Writhed not at passèd joy?
                    To know the change and feel it,
                       When there is none to heal it,
                    Nor numbèd sense to steal it,
                       Was never said in rhyme.