Pollen Beetles are small blackish beetles with a metallic sheen.  They are usually attracted to yellow flowers, such as buttercups, dandelions and oil-seed rape, but also to any yellow object, and can be very common.  The commonest is Meligethes aeneus, but there are many different species, and identification is very difficult requiring examination of the male genitalia.

If you haven't identifed the species of pollen beetle from a specimen using standard keys, you should record it as 'Meligethes'.  Unless identified by a recognised expert, good photos are required. State the beetle's size in the comments box