Yes. Arcane magic relies heavily on magrams [1]-- glyphs, runes and patterns that hold special power. These mystical schemas have the power to entrap lei and hold it within.
Wizards thus learn to imprint magrams in their mind, turning their own mind into lei trap. The more they know and keep in mind, the more spell slots they have. In fact, each spell slot for a wizard is a different magram.
They are built serially, becoming more and more complex. The first level, known as sepis, only has simple, basic shapes -- just enough to hold cantrips.
Spells also are magrams, but they're far more complicated, as they are tri-dimensional instead of bi-dimensional. Therefore, they cannot be transcribed as easily and require lots of pages in a spellbook -- or the special techniques of a Geometer (see Complete Arcane).
Wizards, when preparing a spell, are mentally unfolding one of their magrams into the tridimensional shape of a spell. It is a difficult mental exercise, as they have to keep in mind every single triangles, rhombus, radiant, circle, lines, harmonics, and pattern as he picture the unfolding in his mind. It is easier to do this work sequentially, which explains why preparing just one spell takes 15 minutes [2], while preparing several spells takes, at most, 60 minutes.
When casting a spell, Wizards unleash the stored lei out of their mind, but force it to keep its shape. With a good mystical sight [3], it is possible to see the lei of the cast spell seemingly as strands of golden light tangled up in a complicated, convoluted shape. When several spells are coexisting on a same location or creature, the strands can get all snarled up and make for a greater, stronger whole if done right. Spellcasters who know how to do this are often said to be weaving or knitting spells together. [4]
So, yes, runes are important for magic, at least for arcane magic. Sorcerers do what wizards do, but on a subconscious level, they seldom have knowledge of the intellectual efforts their mind are making. It comes to them naturally, while wizards have to learn it.
As for bards, they do the exact same thing as wizards, but with sounds rather than symbols. Cunning scholars have noticed that wizards use many musical words to refer to spellcasting, such as harmonics or tessitura. It is believed by them that music is just another medium to transcribe magrams (as well as less potent symbols), to transcribe them in an ephemeral, sequential way rather than in a solid, instantaneous way like glyphs are. After all, they say, nearly anyone is able to convey emotions through song or music, and what are emotions, if not mental patterns?
1: Made up word with a blatant etymology: magic gram (as in diagram, engram, etc., not as milligram).
2: Preparing a single spell takes, IMC, 10+spell level minutes. Preparing several spells takes 10+highest spell level+number of spells, maximum 60.
3: I have kept the Scry skill. It represents this mystical sight, and can be used, outside of scrying, to a number of special sight abilities, such as seeing in the Ethereal Plane, noticing lei patterns, or finding dimensional ripples. Scry gives a synergy bonus to Spellcraft to identify a spell being cast, as you can perceive the lei shape moving out of the spellcaster and into the world.
4: In a way, you could liken this to the mythals of the Forgotten Realms -- where magic is called the Weave, by the way. It's a somewhat close idea.
