  Motivated by recent experiments, we investigate the quantum spin Hall state
in 2D topological insulator/ferromagnetic metal planar junctions by means of a
tight-binding model and linear response theory. We demonstrate that whether the
edge state Dirac cone is submerged into the ferromagnetic subbands and the
direction of the magnetization dramatically affect (i) how the edge state
percolates into the ferromagnet, and (ii) the spin-momentum locking of the edge
state. Laminar flows of room temperature persistent charge and spin currents
near the interface are uncovered. In addition, the current-induced spin
polarization at the edge of the 2D topological insulator is found to be
dramatically enhanced near the impurities. The current-induced spin
polarization in the ferromagnet is mainly polarized in the out-of-plane
direction ${\hat{\bf z}}$, rendering a current-induced spin torque that is
predominantly field-like $\propto {\bf S}\times{\hat{\bf z}}$.
