Transformation of the object may appear to be an esoteric phrase, but that's precisely what happens when commonplace things are changed into art and given levels of meaning beyond their outward appearances.

To copy things exactly as they appear is a craft, but to make them metaphorical, symbolic and memorable is art.

Toys may seem a trivial starting point for art, especially when they are the old clumsily cast toys from the World War II era.

Often there was almost no detail - wheels without even black tyres, and axles of wire that bent and left the wheels like the lamest of ducks - and they were dipped in thick paint which soon flaked off.

All these things are perfectly captured in a series of paintings by Peter Miller called Stuck in Traffic, on at the McPherson Gallery until June 3. The exhibition is entirely of paintings of these crude toys, that would be spurned by any modern child.

These are not just nostalgic illustrations but powerful evocations of a time and, even more, of the passing of time - and a sense of mortality.

Miller says he is influenced by Dutch vanitas painters of the 16th and 17th centuries, but instead of a skull, hourglass and a burned-out candle he paints an old rough toy bus without wheels and whose blank windows really look like a skull.

This is serious stuff, but there is a playful element. These are, after all, toys. They show signs of being used and banged about. Certainly they would evoke memories for the middle-aged and elderly. They are exactly painted and exist as lively images in their own right and yet are able to carry the weight of metaphor.

It is a highly individual exhibition which surprises by evocative levels of underlying meaning.

There are skulls, too, in the work of Pete Wheeler in Home Before Dark at Whitespace Gallery until May 27.

Wheeler is also a skilful handler of paint, working on a large scale with firm, decisive brush-strokes. He is quite capable of modelling the hollow rotundity of a skull, even one disfigured by blows, as he is at painting the heavy fur of a ravenous wolf.

The skulls are painted in rank on horrid rank in Green Skulls and - with greater effect - in Skulls, where they are buried in snow. These bony objects are not just symbols of time passing but of cruelty and oppression.

The themes are reinforced when the objects in the paintings are hands reaching through bars.

Sometimes the symbolism works but at other times its impact is lessened. For instance, the portrait Johnny? Cash is just a picture of some glum man. Yet when the artist paints Small Hand as a landscape of ridges we feel the unity between humanity and the world.

The most evocative image is the painting of a wolf. Here there is not much colour but what there is has a telling effect - yellow eyes and a glimpse of red tongue. The picture of a wolf is transformed into the painting of a predator.

The exhibition, which is not comfortable, is the work of a politically involved painter and the works are accomplished enough to show a serious artist at work.

Sriwhana Spong, already an award-winning young artist, has a show called Candlestick Park at the Anna Miles Gallery until May 27. She, too, concentrates on objects but uses them in a variety of media. The objects evoke her past and also convert her present reality into art.

Simple things - such as hedges in her garden, and flags - are part of the images recorded on DVD in a work projected on the gallery wall.

Candlestick Park, a big stadium in San Francisco, is where the Beatles gave their last concert. Obliquely, Spong converts this into images of hedges and closed doors, all done with heavy shadows and the atmosphere of a black and white movie.

Flags and bunting cast their shadows on the paths between the hedges. The result is to create sad and celebratory images of passing and present memory.

The same complexities apply to a curious little wall sculpture which has Indonesian brass bells of antique shape dangling from support made from flattened Coca-Cola cans.

Sticks from Spong's garden are polished and delicately painted to transform them into something with a history, although we would have difficulty associating them with Wuthering Heights, to which we are told they refer.

Changes and contradictions are also recorded in batik banners that acknowledge Spong's Indonesian background.

A photograph of a shrine in a garden brings together a multiplicity of objects. Rods, flags and sculptures from elsewhere in the show have been translated into cult objects of worship, although the meaning is only partly resolved. This is the work of an artist with great powers of invention but tangled in obscurities.