The energy of interaction of a normal helium atom and one excited to the first triplet or singlet metastable state is calculated over a range of nuclear separations from
a
0
to 12
a
0
. The Heitler-London method is followed, with inclusion of all non-orthogonality integrals, and using analytic wave functions. Because of identity of the nuclei,
g
and
u
states of interaction occur, the energy of the
u
state having a minimum at about 2·1
a
0
, and a positive maximum of 0·29 and 0·26 eV (for triplet and singlet states respectively) at about 4
a
0
; the
g
state is entirely repulsive. Comparison is made with experimental evidence for the binding energy of normal and metastable (triplet) atoms. An estimate is made of the second-order dipole-dipole interaction for large separations, and it seems certain that the first-order interaction dominates at least to 12
a
0
. Methods of calculating the necessary integrals are discussed in an appendix.
Exact closed-form analytic wave functions in two dimensions: Contact-interacting fermionic spinful ultracold atoms in a rapidly rotating trap