Beetles are the largest insect order (Coleoptera), numbering thousands of species in Canada alone. You will see many of them on flowers, though the majority of beetles are not floral visitors. Beetles with smooth bodies are not effective pollinators, but those with hairy bodies can carry pollen between flowers.
Beetles visit flowers for many reasons. Some are truly interested in pollen and nectar as a food source, as are the other major pollinating insects, but some prefer to eat the flowers themselves, or other insects. Predatory beetles often hide within flowers, waiting for soft-bodied flies to visit. Some, such as ladybeetles, visit flowers to feed on small pests such as aphids, though they may also consume some nectar as a kind of “fast food”.
Beetles are generally clumsy and rough, compared to the more delicate butterflies and aerodynamic flies. Beetles tend to visit large, heavily-constructed flowers that are either flat or bowl-shaped to give them an easy place to land. Relatively large beetles can often damage flowers, or the pollinating parts of flowers, especially when they feed on pollen with their large cutting mouth parts. However, many flowers resist this damage either by producing many more flowers than necessary, or by enclosing their reproductive organs deep within their corollas.