  Deuteron elastic and deep inelastic electromagnetic properties have been
studied within the front-form Hamiltonian dynamics, using a
Poincar\'e-covariant current operator. The deuteron elastic form factors are
strongly sensitive to different realistic $N-N$ interactions, while the
relevance of different nucleon form factor models is huge for $A(Q^2)$, weak
for $B(Q^2)$ and negligible for the tensor polarization. The possibility to
gain information on the neutron charge form factor from an analysis of $A(Q^2)$
has been investigated. The extraction of the neutron structure functions from
the deuteron deep inelastic structure functions at high $x$ is largely affected
by the use of our Poincar\'e-covariant relativistic approach instead of the
usual impulse approximation within an instant-form approach.
