What are four similes in "The Lady of Shalott" by Alfred Lord Tennyson?

If you read the chapter about the Lady of Shalott in
King Arthur and his Knights of the Round Table, it really helps you
understand this poem better.

The simile is a comparison of
two unlike things using the word like or as. 
The trick here is not assuming because these two words are used, a simile is there.  In
this poem, the word as is used often, however there is only one
true simile where as is used.

Here are
the similes:

1.

readability="6">

The gemmy bridle glitter'd free,
Like
to some branch of stars we see
Hung in the golden
Galaxy

In this stanza
Tennyson is comparing Lancelot bridle to a constellation in a golden galaxy.  Clearly,
he is trying to help us see how shiny the bridle must have appeared to the Lady of
Shalott as she watched in her magic
mirror.

2.

readability="6">

The helmet and the helmet-feather

Burn'd like one burning flame
together,

This simile again
demonstrates how striking he must have appeared.  The next simile appears right after
the description of the helmet and helmet
feather:

3.

readability="10">

As he rode down to Camelot.
As often
thro' the purple night,
Below the starry clusters bright,
Some
bearded meteor, burning bright,
Moves over still
Shalott.

This comparison
compares Lancelot's ride through Camelot to a meteor streaks through a purple sky.  Note
the word as is used to create this
comparison.

4.

readability="7">

And down the river's dim expanse
Like
some bold seer in a trance,
Seeing all his own mischance --
With a
glassy countenance
Did she look to
Camelot.

The Lady of Shalott,
realizing that Lancelot loves another, prepares to die knowing that if she leaves
Camelot the curse will kill her.  Knowing she will never have Lancelot, she does so
anyway.