If you touch the insulation you'll be fine.
If you touch one of the conductors you will not be fine.

Luckily while the service lines have a huge current available, they are still only 120 V to ground (and 240 V between them).

Just avoid nicking or damaging the insulation on them.

Shorting them out to ground is a REAL hazard.

The arc and flash can be huge.

Watch out that NOTHING (tools, other wires) contacts the bare conductors.

I remember helping someone replace a panel before I had any electrical experience myself who 'knew what they were doing.' They just taped the entrance cables and said 'that will be good enough' and when he was jerking.. I am not joking jerking on the old box to get it off the entrance cable the tape came off. We had been standing in a dark utility room area of the basement which became lit like like 1,000 of them flashing firecrackers. He called and had the meter pulled after that event.