  The Sun is used as the fundamental standard in chemical abundance studies,
thus it is important to know whether the solar abundance pattern is
representative of the solar neighborhood. Albeit at low precision (0.05 - 0.10
dex) the Sun seems to be a typical solar-metallicity disk star, at high
precision (0.01 dex) its abundance pattern seems abnormal when compared to
solar twins. The Sun shows a deficiency of refractory elements that could be
due to the formation of terrestrial planets. The formation of giant planets may
also introduce a signature in the chemical composition of stars. We discuss
both planet signatures and also the enhancement of neutron-capture elements in
the solar twin 18 Sco.
