As we know PVST runs seperate STP instances per VLAN, whch makes some ports in "Forward" state in some VLANs & blocking in others, hence we can achieve kind of load-balancing of traffic
Similar thing can be achieved in MSTP as-well.
By default when you enable MSTP, only one 'instance' is running which spans on VLANS on the system.
For better load-balancing of traffic, you can create multiple MST "instances": via something called as "instance VLAN mapping"
This needs bit planning & deciding a root-bridge for each of those instances for "optimal" topology.
Sample config like below needs to be configured on all the switches in your topology
(IDF-1) (config) #mstp
(IDF-1) (Global MSTP) #region-name REG-1
(IDF-1) (Global MSTP) #instance 0 bridge-priority 16384
(IDF-1) (Global MSTP) #instance 1 bridge-priority 32768
(IDF-1) (Global MSTP) #instance 2 bridge-priority 16384
(IDF-1) (Global MSTP) #instance 1 vlan 100,200
(IDF-1) (Global MSTP) #instance 2 vlan 300,400
Above config makes VLAN 100,200 as part of MSTP "instance 1", and so on....
And bridge-priority needs to be varied on other switches. In short, Bridge-priority (lower) decides which switch will be root-bridge for specific instance, (Refer MAS documentation for more details...)